PHP 7.0.6 Released

    preg_replace

    (PHP 4, PHP 5, PHP 7)

    preg_replace — Perform a regular expression search and replace

    Description

    mixed preg_replace ( mixed $pattern , mixed $replacement , mixed $subject [, int $limit = -1 [, int &$count ]] )

    Searches subject for matches to pattern and replaces them with replacement.

    Parameters

    pattern

    The pattern to search for. It can be either a string or an array with strings.

    Several PCRE modifiers are also available.

    replacement

    The string or an array with strings to replace. If this parameter is a string and the pattern parameter is an array, all patterns will be replaced by that string. If both pattern and replacement parameters are arrays, each pattern will be replaced by the replacement counterpart. If there are fewer elements in the replacement array than in the pattern array, any extra patterns will be replaced by an empty string.

    replacement may contain references of the form \\n or (since PHP 4.0.4) $n, with the latter form being the preferred one. Every such reference will be replaced by the text captured by the n'th parenthesized pattern. n can be from 0 to 99, and \\0 or $0 refers to the text matched by the whole pattern. Opening parentheses are counted from left to right (starting from 1) to obtain the number of the capturing subpattern. To use backslash in replacement, it must be doubled ("\\\\" PHP string).

    When working with a replacement pattern where a backreference is immediately followed by another number (i.e.: placing a literal number immediately after a matched pattern), you cannot use the familiar \\1 notation for your backreference. \\11, for example, would confuse preg_replace() since it does not know whether you want the \\1 backreference followed by a literal 1, or the \\11 backreference followed by nothing. In this case the solution is to use \${1}1. This creates an isolated $1 backreference, leaving the 1 as a literal.

    When using the deprecated e modifier, this function escapes some characters (namely ', ", \ and NULL) in the strings that replace the backreferences. This is done to ensure that no syntax errors arise from backreference usage with either single or double quotes (e.g. 'strlen(\'$1\')+strlen("$2")'). Make sure you are aware of PHP's string syntax to know exactly how the interpreted string will look.

    subject

    The string or an array with strings to search and replace.

    If subject is an array, then the search and replace is performed on every entry of subject, and the return value is an array as well.

    limit

    The maximum possible replacements for each pattern in each subject string. Defaults to -1 (no limit).

    count

    If specified, this variable will be filled with the number of replacements done.

    Return Values

    preg_replace() returns an array if the subject parameter is an array, or a string otherwise.

    If matches are found, the new subject will be returned, otherwise subject will be returned unchanged or NULL if an error occurred.

    Errors/Exceptions

    As of PHP 5.5.0 E_DEPRECATED level error is emitted when passing in the "\e" modifier. As of PHP 7.0.0 E_WARNING is emited in this case and "\e" modifier has no effect.

    Changelog

    Version Description
    7.0.0 Support for the /e modifier has been removed. Use preg_replace_callback() instead.
    5.5.0 The /e modifier is deprecated. Use preg_replace_callback() instead. See the PREG_REPLACE_EVAL documentation for additional information about security risks.
    5.1.0 Added the count parameter

    Examples

    Example #1 Using backreferences followed by numeric literals

    <?php
    $string     = 'April 15, 2003';
    $pattern = '/(\w+) (\d+), (\d+)/i';
    $replacement = '${1}1,$3';
    echo     preg_replace($pattern, $replacement, $string);
    ?>

    The above example will output:

    April1,2003

    Example #2 Using indexed arrays with preg_replace()

    <?php
    $string     = 'The quick brown fox jumps over the lazy dog.';
    $patterns = array();
    $patterns[0] = '/quick/';
    $patterns[1] = '/brown/';
    $patterns[2] = '/fox/';
    $replacements = array();
    $replacements[2] = 'bear';
    $replacements[1] = 'black';
    $replacements[0] = 'slow';
    echo     preg_replace($patterns, $replacements, $string);
    ?>

    The above example will output:

    The bear black slow jumps over the lazy dog.

    By ksorting patterns and replacements, we should get what we wanted.

    <?php
    ksort    ($patterns);
    ksort($replacements);
    echo     preg_replace($patterns, $replacements, $string);
    ?>

    The above example will output:

    The slow black bear jumps over the lazy dog.

    Example #3 Replacing several values

    <?php
    $patterns     = array ('/(19|20)(\d{2})-(\d{1,2})-(\d{1,2})/',
                           '/^\s*{(\w+)}\s*=/');
    $replace = array ('\3/\4/\1\2', '$\1 =');
    echo     preg_replace($patterns, $replace, '{startDate} = 1999-5-27');
    ?>

    The above example will output:

    $startDate = 5/27/1999

    Example #4 Strip whitespace

    This example strips excess whitespace from a string.

    <?php
    $str     = 'foo   o';
    $str = preg_replace('/\s\s+/', ' ', $str);
    // This will be 'foo o' now
    echo $str;
    ?>

    Example #5 Using the count parameter

    <?php
    $count     = 0;

    echo     preg_replace(array('/\d/', '/\s/'), '*', 'xp 4 to', -1 , $count);
    echo     $count; //3
    ?>

    The above example will output:

    xp***to
3

    Notes

    Note:

    When using arrays with pattern and replacement, the keys are processed in the order they appear in the array. This is not necessarily the same as the numerical index order. If you use indexes to identify which pattern should be replaced by which replacement, you should perform a ksort() on each array prior to calling preg_replace().

    See Also

    User Contributed Notes

    arkani at iol dot pt
    7 years ago
    Because i search a lot 4 this:

    The following should be escaped if you are trying to match that character

    \ ^ . $ | ( ) [ ]
    * + ? { } ,

    Special Character Definitions
    \ Quote the next metacharacter
    ^ Match the beginning of the line
    . Match any character (except newline)
    $ Match the end of the line (or before newline at the end)
    | Alternation
    () Grouping
    [] Character class
    * Match 0 or more times
    + Match 1 or more times
    ? Match 1 or 0 times
    {n} Match exactly n times
    {n,} Match at least n times
    {n,m} Match at least n but not more than m times
    More Special Character Stuff
    \t tab (HT, TAB)
    \n newline (LF, NL)
    \r return (CR)
    \f form feed (FF)
    \a alarm (bell) (BEL)
    \e escape (think troff) (ESC)
    \033 octal char (think of a PDP-11)
    \x1B hex char
    \c[ control char
    \l lowercase next char (think vi)
    \u uppercase next char (think vi)
    \L lowercase till \E (think vi)
    \U uppercase till \E (think vi)
    \E end case modification (think vi)
    \Q quote (disable) pattern metacharacters till \E
    Even More Special Characters
    \w Match a "word" character (alphanumeric plus "_")
    \W Match a non-word character
    \s Match a whitespace character
    \S Match a non-whitespace character
    \d Match a digit character
    \D Match a non-digit character
    \b Match a word boundary
    \B Match a non-(word boundary)
    \A Match only at beginning of string
    \Z Match only at end of string, or before newline at the end
    \z Match only at end of string
    \G Match only where previous m//g left off (works only with /g)
    logofero at gmail dot com
    1 year ago
    Why not offset parameter to replace the string? It would be helpful

    example:

    mixed preg_replace (mixed $pattern, mixed $replacement, mixed $subject [, int $limit = -1 [, int & $count [, int $offset = 0]]])

    1 $pattern
    2 $replacement
    3 $subject
    4 $limit
    5 $count
    6 $offset <- it is planned?
    hello at weblap dot ro
    6 years ago
    Post slug generator, for creating clean urls from titles.
    It works with many languages.

    <?php
    function remove_accent($str)
    {
          $a = array('À', 'Á', 'Â', 'Ã', 'Ä', 'Å', 'Æ', 'Ç', 'È', 'É', 'Ê', 'Ë', 'Ì', 'Í', 'Î', 'Ï', 'Ð', 'Ñ', 'Ò', 'Ó', 'Ô', 'Õ', 'Ö', 'Ø', 'Ù', 'Ú', 'Û', 'Ü', 'Ý', 'ß', 'à', 'á', 'â', 'ã', 'ä', 'å', 'æ', 'ç', 'è', 'é', 'ê', 'ë', 'ì', 'í', 'î', 'ï', 'ñ', 'ò', 'ó', 'ô', 'õ', 'ö', 'ø', 'ù', 'ú', 'û', 'ü', 'ý', 'ÿ', 'Ā', 'ā', 'Ă', 'ă', 'Ą', 'ą', 'Ć', 'ć', 'Ĉ', 'ĉ', 'Ċ', 'ċ', 'Č', 'č', 'Ď', 'ď', 'Đ', 'đ', 'Ē', 'ē', 'Ĕ', 'ĕ', 'Ė', 'ė', 'Ę', 'ę', 'Ě', 'ě', 'Ĝ', 'ĝ', 'Ğ', 'ğ', 'Ġ', 'ġ', 'Ģ', 'ģ', 'Ĥ', 'ĥ', 'Ħ', 'ħ', 'Ĩ', 'ĩ', 'Ī', 'ī', 'Ĭ', 'ĭ', 'Į', 'į', 'İ', 'ı', 'IJ', 'ij', 'Ĵ', 'ĵ', 'Ķ', 'ķ', 'Ĺ', 'ĺ', 'Ļ', 'ļ', 'Ľ', 'ľ', 'Ŀ', 'ŀ', 'Ł', 'ł', 'Ń', 'ń', 'Ņ', 'ņ', 'Ň', 'ň', 'ʼn', 'Ō', 'ō', 'Ŏ', 'ŏ', 'Ő', 'ő', 'Œ', 'œ', 'Ŕ', 'ŕ', 'Ŗ', 'ŗ', 'Ř', 'ř', 'Ś', 'ś', 'Ŝ', 'ŝ', 'Ş', 'ş', 'Š', 'š', 'Ţ', 'ţ', 'Ť', 'ť', 'Ŧ', 'ŧ', 'Ũ', 'ũ', 'Ū', 'ū', 'Ŭ', 'ŭ', 'Ů', 'ů', 'Ű', 'ű', 'Ų', 'ų', 'Ŵ', 'ŵ', 'Ŷ', 'ŷ', 'Ÿ', 'Ź', 'ź', 'Ż', 'ż', 'Ž', 'ž', 'ſ', 'ƒ', 'Ơ', 'ơ', 'Ư', 'ư', 'Ǎ', 'ǎ', 'Ǐ', 'ǐ', 'Ǒ', 'ǒ', 'Ǔ', 'ǔ', 'Ǖ', 'ǖ', 'Ǘ', 'ǘ', 'Ǚ', 'ǚ', 'Ǜ', 'ǜ', 'Ǻ', 'ǻ', 'Ǽ', 'ǽ', 'Ǿ', 'ǿ');
          $b = array('A', 'A', 'A', 'A', 'A', 'A', 'AE', 'C', 'E', 'E', 'E', 'E', 'I', 'I', 'I', 'I', 'D', 'N', 'O', 'O', 'O', 'O', 'O', 'O', 'U', 'U', 'U', 'U', 'Y', 's', 'a', 'a', 'a', 'a', 'a', 'a', 'ae', 'c', 'e', 'e', 'e', 'e', 'i', 'i', 'i', 'i', 'n', 'o', 'o', 'o', 'o', 'o', 'o', 'u', 'u', 'u', 'u', 'y', 'y', 'A', 'a', 'A', 'a', 'A', 'a', 'C', 'c', 'C', 'c', 'C', 'c', 'C', 'c', 'D', 'd', 'D', 'd', 'E', 'e', 'E', 'e', 'E', 'e', 'E', 'e', 'E', 'e', 'G', 'g', 'G', 'g', 'G', 'g', 'G', 'g', 'H', 'h', 'H', 'h', 'I', 'i', 'I', 'i', 'I', 'i', 'I', 'i', 'I', 'i', 'IJ', 'ij', 'J', 'j', 'K', 'k', 'L', 'l', 'L', 'l', 'L', 'l', 'L', 'l', 'l', 'l', 'N', 'n', 'N', 'n', 'N', 'n', 'n', 'O', 'o', 'O', 'o', 'O', 'o', 'OE', 'oe', 'R', 'r', 'R', 'r', 'R', 'r', 'S', 's', 'S', 's', 'S', 's', 'S', 's', 'T', 't', 'T', 't', 'T', 't', 'U', 'u', 'U', 'u', 'U', 'u', 'U', 'u', 'U', 'u', 'U', 'u', 'W', 'w', 'Y', 'y', 'Y', 'Z', 'z', 'Z', 'z', 'Z', 'z', 's', 'f', 'O', 'o', 'U', 'u', 'A', 'a', 'I', 'i', 'O', 'o', 'U', 'u', 'U', 'u', 'U', 'u', 'U', 'u', 'U', 'u', 'A', 'a', 'AE', 'ae', 'O', 'o');
      return     str_replace($a, $b, $str);
    }

    function     post_slug($str)
    {
      return     strtolower(preg_replace(array('/[^a-zA-Z0-9 -]/', '/[ -]+/', '/^-|-$/'),
      array(    '', '-', ''), remove_accent($str)));
    }
    ?>

    Example: post_slug(' -Lo#&@rem  IPSUM //dolor-/sit - amet-/-consectetur! 12 -- ')
    will output: lorem-ipsum-dolor-sit-amet-consectetur-12
    denis_truffaut a t hotmail d o t com
    4 years ago
    If you want to catch characters, as well european, russian, chinese, japanese, korean of whatever, just :
    - use mb_internal_encoding('UTF-8');
    - use preg_replace('`...`u', '...', $string) with the u (unicode) modifier

    For further information, the complete list of preg_* modifiers could be found at :
    http://php.net/manual/en/reference.pcre.pattern.modifiers.php
    Alexey Lebedev
    9 years ago
    Wasted several hours because of this:

    <?php
    $str    ='It&#039;s a string with HTML entities';
    preg_replace('~&#(\d+);~e', 'code2utf($1)', $str);
    ?>

    This code must convert numeric html entities to utf8. And it does with a little exception. It treats wrong codes starting with &#0

    The reason is that code2utf will be called with leading zero, exactly what the pattern matches - code2utf(039).
    And it does matter! PHP treats 039 as octal number.
    Try <?php print(011); ?>

    Solution:
    <?php preg_replace('~&#0*(\d+);~e', 'code2utf($1)', $str); ?>
    Jeroen
    1 year ago
    Hello there,
    I would like to share a regex (PHP) sniplet of code
    I wrote (2012) for myself it is also being used in the
    Yerico sriptmerge plugin for joomla marked as simple code..
    To  compress javascript code and remove all comments from it.
    It also works with mootools It is fast...
    (in compairison to other PHP solutions) and does not damage the
    Javascript it self and it resolves lots of comment removal isseus.

    //START Remove comments.

       $buffer = str_replace('/// ', '///', $buffer);       
       $buffer = str_replace(',//', ', //', $buffer);
       $buffer = str_replace('{//', '{ //', $buffer);
       $buffer = str_replace('}//', '} //', $buffer);
       $buffer = str_replace('*//*', '*/  /*', $buffer);
       $buffer = str_replace('/**/', '/*  */', $buffer);
       $buffer = str_replace('*///', '*/ //', $buffer);
       $buffer = preg_replace("/\/\/.*\n\/\/.*\n/", "", $buffer);
       $buffer = preg_replace("/\s\/\/\".*/", "", $buffer);
       $buffer = preg_replace("/\/\/\n/", "\n", $buffer);
       $buffer = preg_replace("/\/\/\s.*.\n/", "\n  \n", $buffer);
       $buffer = preg_replace('/\/\/w[^w].*/', '', $buffer);
       $buffer = preg_replace('/\/\/s[^s].*/', '', $buffer);
       $buffer = preg_replace('/\/\/\*\*\*.*/', '', $buffer);
       $buffer = preg_replace('/\/\/\*\s\*\s\*.*/', '', $buffer);
       $buffer = preg_replace('/[^\*]\/\/[*].*/', '', $buffer);
       $buffer = preg_replace('/([;])\/\/.*/', '$1', $buffer);
       $buffer = preg_replace('/((\r)|(\n)|(\R)|([^0]1)|([^\"]\s*\-))(\/\/)(.*)/', '$1', $buffer);
       $buffer = preg_replace("/([^\*])[\/]+\/\*.*[^a-zA-Z0-9\s\-=+\|!@#$%^&()`~\[\]{};:\'\",<.>?]/", "$1", $buffer);
      $buffer = preg_replace("/\/\*/", "\n/*dddpp", $buffer);
      $buffer = preg_replace('/((\{\s*|:\s*)[\"\']\s*)(([^\{\};\"\']*)dddpp)/','$1$4', $buffer);
      $buffer = preg_replace("/\*\//", "xxxpp*/\n", $buffer);
      $buffer = preg_replace('/((\{\s*|:\s*|\[\s*)[\"\']\s*)(([^\};\"\']*)xxxpp)/','$1$4', $buffer);
      $buffer = preg_replace('/([\"\'])\s*\/\*/', '$1/*', $buffer);
      $buffer = preg_replace('/(\n)[^\'"]?\/\*dddpp.*?xxxpp\*\//s', '', $buffer);
      $buffer = preg_replace('/\n\/\*dddpp([^\s]*)/', '$1', $buffer);
      $buffer = preg_replace('/xxxpp\*\/\n([^\s]*)/', '*/$1', $buffer);
      $buffer = preg_replace('/xxxpp\*\/\n([\"])/', '$1', $buffer);
      $buffer = preg_replace('/(\*)\n*\s*(\/\*)\s*/', '$1$2$3', $buffer);
      $buffer = preg_replace('/(\*\/)\s*(\")/', '$1$2', $buffer);
      $buffer = preg_replace('/\/\*dddpp(\s*)/', '/*', $buffer);
      $buffer = preg_replace('/\n\s*\n/', "\n", $buffer);
      $buffer = preg_replace("/([^\'\"]\s*)<!--.*-->(?!(<\/div>)).*/","$1", $buffer);
      $buffer = preg_replace('/([^\n\w\-=+\|!@#$%^&*()`~\[\]{};:\'",<.>\/?\\\\])(\/\/)(.*)/', '$1', $buffer);

    //END Remove comments.   

    //START Remove all whitespaces

      $buffer = preg_replace('/\s+/', ' ', $buffer);
      $buffer = preg_replace('/\s*(?:(?=[=\-\+\|%&\*\)\[\]\{\};:\,\.\<\>\!\@\#\^`~]))/', '', $buffer);
      $buffer = preg_replace('/(?:(?<=[=\-\+\|%&\*\)\[\]\{\};:\,\.\<\>\?\!\@\#\^`~]))\s*/', '', $buffer);
      $buffer = preg_replace('/([^a-zA-Z0-9\s\-=+\|!@#$%^&*()`~\[\]
    {};:\'",<.>\/?])\s+([^a-zA-Z0-9\s\-=+\|!@#$%^&*()`~\[\]
    {};:\'",<.>\/?])/', '$1$2', $buffer);

    //END Remove all whitespaces

    I am off coarse not a programmer just wanted to
    make the plugin work like i wanted it to....
    (NOTE:
    For the webmaster sorry I posted this in the wrong topic before...)
    timitheenchanter
    4 years ago
    If you have issues where preg_replace returns an empty string, please take a look at these two ini parameters:

    pcre.backtrack_limit
    pcre.recursion_limit

    The default is set to 100K.  If your buffer is larger than this, look to increase these two values.
    dani dot church at gmail dot youshouldknowthisone
    9 years ago
    Note that it is in most cases much more efficient to use preg_replace_callback(), with a named function or an anonymous function created with create_function(), instead of the /e modifier.  When preg_replace() is called with the /e modifier, the interpreter must parse the replacement string into PHP code once for every replacement made, while preg_replace_callback() uses a function that only needs to be parsed once.
    spamthishard at wtriple dot com
    2 years ago
    If you want to replace only the n-th occurrence of $pattern, you can use this function:

    <?php

    function preg_replace_nth($pattern, $replacement, $subject, $nth=1) {
        return     preg_replace_callback($pattern,
            function(    $found) use (&$pattern, &$replacement, &$nth) {
                        $nth--;
                    if (    $nth==0) return preg_replace($pattern, $replacement, reset($found) );
                    return     reset($found);
            },     $subject,$nth  );
    }

    echo     preg_replace_nth("/(\w+)\|/", '${1} is the 4th|', "|aa|b|cc|dd|e|ff|gg|kkk|", 4);

    ?>

    this outputs |aa|b|cc|dd is the 4th|e|ff|gg|kkk|
    backreferences are accepted in $replacement
    php-comments-REMOVE dot ME at dotancohen dot com
    8 years ago
    Below is a function for converting Hebrew final characters to their
    normal equivelants should they appear in the middle of a word.
    The /b argument does not treat Hebrew letters as part of a word,
    so I had to work around that limitation.

    <?php

    $text    ="עברית מבולגנת";

    function     hebrewNotWordEndSwitch ($from, $to, $text) {
           $text=
            preg_replace('/'.$from.'([א-ת])/u','$2'.$to.'$1',$text);
       return     $text;
    }

    do {
           $text_before=$text;
           $text=hebrewNotWordEndSwitch("ך","כ",$text);
           $text=hebrewNotWordEndSwitch("ם","מ",$text);
           $text=hebrewNotWordEndSwitch("ן","נ",$text);
           $text=hebrewNotWordEndSwitch("ף","פ",$text);
           $text=hebrewNotWordEndSwitch("ץ","צ",$text);
    }   while (     $text_before!=$text );

    print     $text; // עברית מסודרת!

    ?>

    The do-while is necessary for multiple instances of letters, such
    as "אנני" which would start off as "אןןי". Note that there's still the
    problem of acronyms with gershiim but that's not a difficult one
    to solve. The code is in use at http://gibberish.co.il which you can
    use to translate wrongly-encoded Hebrew, transliterize, and some
    other Hebrew-related functions.

    To ensure that there will be no regular characters at the end of a
    word, just convert all regular characters to their final forms, then
    run this function. Enjoy!
    Terminux (dot) anonymous at gmail
    5 years ago
    This function will strip all the HTML-like content in a string.
    I know you can find a lot of similar content on the web, but this one is simple, fast and robust. Don't simply use the built-in functions like strip_tags(), they dont work so good.

    Careful however, this is not a correct validation of a string ; you should use additional functions like mysql_real_escape_string and filter_var, as well as custom tests before putting a submission into your database.

    <?php

    $html     = <<<END
    <div id="function.preg-split" class="refentry"> Bonjour1 \t
    <div class="refnamediv"> Bonjour2 \t
    <h1 class="refname">Bonjour3 \t</h1>
    <h1 class=""">Bonjour4 \t</h1>
    <h1 class="*%1">Bonjour5 \t</h1>
    <body>Bonjour6 \t<//body>>
    </ body>Bonjour7 \t<////        body>>
    <
    a href="image.php" alt="trans" /        >
    some leftover text...
         < DIV class=noCompliant style = "text-align:left;" >
    ... and some other ...
    < dIv > < empty>  </ empty>
      <p> This is yet another text <br  >
         that wasn't <b>compliant</b> too... <br   />
         </p>
    <div class="noClass" > this one is better but we don't care anyway </div ><P>
        <input   type= "text"  name ='my "name' value  = "nothin really." readonly>
    end of paragraph </p> </Div>   </div>   some trailing text
    END;

    // This echoes correctly all the text that is not inside HTML tags
    $html_reg = '/<+\s*\/*\s*([A-Z][A-Z0-9]*)\b[^>]*\/*\s*>+/i';
    echo     htmlentities( preg_replace( $html_reg, '', $html ) );

    // This extracts only a small portion of the text
    echo htmlentities(strip_tags($html));

    ?>
    Ray dot Paseur at SometimesUsesGmail dot com
    4 years ago
    Please see Example #4 Strip whitespace.  This works as designed, but if you are using Windows, it may not work as expected.  The potential "gotcha" is the CR/LF line endings.  On a Unix system, where there is only a single character line ending, that regex pattern will preserve line endings.  On Windows, it may strip line endings.
    nospam at probackup dot nl
    5 years ago
    Warning: a common made mistake in trying to remove all characters except numbers and letters from a string, is to use code with a regex similar to preg_replace('[^A-Za-z0-9_]', '', ...). The output goes in an unexpected direction in case your input contains two double quotes.

    echo preg_replace('[^A-Za-z0-9_]', '', 'D"usseldorfer H"auptstrasse')

    D"usseldorfer H"auptstrasse

    It is important to not forget a leading an trailing forward slash in the regex:

    echo preg_replace('/[^A-Za-z0-9_]/', '', 'D"usseldorfer H"auptstrasse')

    Dusseldorfer Hauptstrasse

    PS An alternative is to use preg_replace('/\W/', '', $t) for keeping all alpha numeric characters including underscores.
    dyer85 at gmail dot com
    7 years ago
    There seems to be some unexpected behavior when using the /m modifier when the line terminators are win32 or mac format.

    If you have a string like below, and try to replace dots, the regex won't replace correctly:

    <?php
    $s     = "Testing, testing.\r\n"
           . "Another testing line.\r\n"
           . "Testing almost done.";

    echo     preg_replace('/\.$/m', '.@', $s); // only last . replaced
    ?>

    The /m modifier doesn't seem to work properly when CRLFs or CRs are used. Make sure to convert line endings to LFs (*nix format) in your input string.
    anyvie at devlibre dot fr
    4 years ago
    A variable can handle a huge quantity of data but preg_replace can't.

    Example :
    <?php
    $url     = "ANY URL WITH LOTS OF DATA";

    // We get all the data into $data
    $data = file_get_contents($url);

    // We just want to keep the content of <head>
    $head = preg_replace("#(.*)<head>(.*?)</head>(.*)#is", '$2', $data);
    ?>

    $head can have the desired content, or be empty, depends on the length of $data.

    For this application, just add :
    $data = substr($data, 0, 4096);
    before using preg_replace, and it will work fine.
    cincodenada at gmail dot dot dot com
    3 years ago
    There seems to be some confusion over how greediness works.  For those familiar with Regular Expressions in other languages, particularly Perl: it works like you would expect, and as documented.  Greedy by default, un-greedy if you follow a quantifier with a question mark.

    There is a PHP/PCRE-specific U pattern modifier that flips the greediness, so that quantifiers are by default un-greedy, and become greedy if you follow the quantifier with a question mark: http://www.php.net/manual/en/reference.pcre.pattern.modifiers.php

    To make things clear, a series of examples:

    <?php

    $preview     = "a bunch of stuff <code>this that</code> and more stuff <code>with a second code block</code> then extra at the end";

    $preview_default = preg_replace('/<code>(.*)<\/code>/is', "<code class=\"prettyprint\">$1</code>", $preview);
    $preview_manually_ungreedy = preg_replace('/<code>(.*?)<\/code>/is', "<code class=\"prettyprint\">$1</code>", $preview);

    $preview_U_default = preg_replace('/<code>(.*)<\/code>/isU', "<code class=\"prettyprint\">$1</code>", $preview);
    $preview_U_manually_greedy = preg_replace('/<code>(.*?)<\/code>/isU', "<code class=\"prettyprint\">$1</code>", $preview);

    echo     "Default, no ?: $preview_default\n";
    echo     "Default, with ?: $preview_manually_ungreedy\n";
    echo     "U flag, no ?: $preview_U_default\n";
    echo     "U flag, with ?: $preview_U_manually_greedy\n";

    ?>

    Results in this:

    Default, no ?: a bunch of stuff <code class="prettyprint">this that</code> and more stuff <code>with a second code block</code> then extra at the end
    Default, with ?: a bunch of stuff <code class="prettyprint">this that</code> and more stuff <code class="prettyprint">with a second code block</code> then extra at the end
    U flag, no ?: a bunch of stuff <code class="prettyprint">this that</code> and more stuff <code class="prettyprint">with a second code block</code> then extra at the end
    U flag, with ?: a bunch of stuff <code class="prettyprint">this that</code> and more stuff <code>with a second code block</code> then extra at the end

    As expected: greedy by default, ? inverts it to ungreedy.  With the U flag, un-greedy by default, ? makes it greedy.
    craiga at craiga dot id dot au
    4 years ago
    If there's a chance your replacement text contains any strings such as "$0.95", you'll need to escape those $n backreferences:

    <?php
    function escape_backreference($x)
    {
        return     preg_replace('/\$(\d)/', '\\\$$1', $x);
    }
    ?>
    akniep at rayo dot info
    7 years ago
    preg_replace (and other preg-functions) return null instead of a string when encountering problems you probably did not think about!
    -------------------------

    It may not be obvious to everybody that the function returns NULL if an error of any kind occurres. An error I happen to stumple about quite often was the back-tracking-limit:
    http://de.php.net/manual/de/pcre.configuration.php
    #ini.pcre.backtrack-limit

    When working with HTML-documents and their parsing it happens that you encounter documents that have a length of over 100.000 characters and that may lead to certain regular-expressions to fail due the back-tracking-limit of above.

    A regular-expression that is ungreedy ("U", http://de.php.net/manual/de/reference.pcre.pattern.modifiers.php) often does the job, but still: sometimes you just need a greedy regular expression working on long strings ...

    Since, an unhandled return-value of NULL usually creates a consecutive error in the application with unwanted and unforeseen consequences, I found the following solution to be quite helpful and at least save the application from crashing:

    <?php

    $string_after     = preg_replace( '/some_regexp/', "replacement", $string_before );

    // if some error occurred we go on working with the unchanged original string
    if (PREG_NO_ERROR !== preg_last_error())
    {
            $string_after = $string_before;
       
            // put email-sending or a log-message here
    } //if

    // free memory
    unset( $string_before );

    ?>

    You may or should also put a log-message or the sending of an email into the if-condition in order to get informed, once, one of your regular-expressions does not have the effect you desired it to have.
    Anonymous
    7 years ago
    People using functions like scandir with user input and protecting against "../" by using preg_replace make sure you run ir recursivly untill preg_match no-long finds it, because if you don't the following can happen.

    If a user gives the path:
    "./....//....//....//....//....//....//....//"
    then your script detects every "../" and removes them leaving:
    "./../../../../../../../"
    Which is proberly going back enough times to show root.

    I just found this vunrability in an old script of mine, which was written several years ago.

    Always do:
    <?php
    while( preg_match( [expression], $input ) )
    {
           $input = preg_replace( [expression], "", $input );
    }
    ?>
    me at perochak dot com
    5 years ago
    If you would like to remove a tag along with the text inside it then use the following code.

    <?php
    preg_replace    ('/(<tag>.+?)+(<\/tag>)/i', '', $string);
    ?>

    example
    <?php $string='<span class="normalprice">55 PKR</span>'; ?>

    <?php
    $string     = preg_replace('/(<span class="normalprice">.+?)+(<\/span>)/i', '', $string);
    ?>

    This will results a null or empty string.

    <?php
    $string    ='My String <span class="normalprice">55 PKR</span>';

    $string = preg_replace('/(<span class="normalprice">.+?)+(<\/span>)/i', '', $string);
    ?>

    This will results a " My String"
    nik at rolls dot cc
    3 years ago
    To split Pascal/CamelCase into Title Case (for example, converting descriptive class names for use in human-readable frontends), you can use the below function:

    <?php
    function expandCamelCase($source) {
      return     preg_replace('/(?<!^)([A-Z][a-z]|(?<=[a-z])[^a-z]|(?<=[A-Z])[0-9_])/', ' $1', $source);
    }
    ?>

    Before:
      ExpandCamelCaseAPIDescriptorPHP5_3_4Version3_21Beta
    After:
      Expand Camel Case API Descriptor PHP 5_3_4 Version 3_21 Beta
    hvishnu999 at gmail dot com
    4 years ago
    To covert a string to SEO friendly, do this:

    <?php
    $realname     = "This is the string to be made SEO friendly!"

    $seoname = preg_replace('/\%/',' percentage',$realname);
    $seoname = preg_replace('/\@/',' at ',$seoname);
    $seoname = preg_replace('/\&/',' and ',$seoname);
    $seoname = preg_replace('/\s[\s]+/','-',$seoname);    // Strip off multiple spaces
    $seoname = preg_replace('/[\s\W]+/','-',$seoname);    // Strip off spaces and non-alpha-numeric
    $seoname = preg_replace('/^[\-]+/','',$seoname); // Strip off the starting hyphens
    $seoname = preg_replace('/[\-]+$/','',$seoname); // // Strip off the ending hyphens
    $seoname = strtolower($seoname);

    echo     $seoname;
    ?>

    This will print: this-is-the-string-to-be-made-seo-friendly
    helia at gmail dot com
    5 months ago
    $pattern='/(09(1|2|3)\d{8})/';
    $string ="n:09138660959 nu: 09371313317 nu:09211313317 n: 09393026988nu:09193472840nnu:09211313317nu:09211313317nu:09121772890";
    $replacements='($1 code $2)';
    echo  preg_replace($pattern, $replacements, $string);
    smcbride at msn dot com
    2 months ago
    A nice and easy way to merge file path strings without worrying about if the path is suffixed with / or the file is prefixed with / is to use preg_replace.  There may be a function to get the endpoints, but this will also fixup any garbage in the middle as well.

    Also...the previous post left out an important character to escape if you want to search for it ... / (slash).

       function mergepath($rootpath, $suffixpath){
          $completepath = $rootpath . "/" . $suffixpath;
          $completepath = preg_replace('/\/+/', '/',, $completepath);
          return $completepath;
       }
    Garrett Albright
    1 year ago
    It may be useful to note that if you pass an associative array as the $replacement parameter, the keys are preserved.

    <?php
    $replaced     = preg_replace('/foo/', 'bar', ['first' => 'foobar', 'second' => 'barfoo']);
    // $replaced is now ['first' => 'barbar', 'second' => 'barbar'].
    ?>
    safranil (at) safranil [dot] fr
    11 months ago
    Warning, preg_replace() has an unexpected behaviour on UTF-8 strings when you use an empty regular expression like "/()/" !

    If you build your regular expression in PHP like this :

    $words = array();
    foreach (explode(" ", $what) as $w)
        if (mb_strlen($w) > 0)
            $words[] = preg_quote($w, "/");
        return preg_replace('/(' . implode("|",$words) . ')/iu', '<span class="text-maroon">\\1</span>', $text);

    Always check if $words array isn't empty :

    if (count($words) == 0)
        return $text;
    elliot dot greene at att dot net
    1 year ago
    preg_replace to only show alpha numeric characters

    $info = "The Development of code . http://www.";

    $info = preg_replace("/[^a-zA-Z0-9]+/", "", $info);

    echo $info;

    OUTPUTS: TheDevelopmentofcodehttpwww

    This is a good workable code
    http://www.sioure.com
    Dustin
    2 years ago
    Matching substrings where the match can exist at the end of the string was non-intuitive to me.

    I found this because:
    strtotime() interprets 'mon' as 'Monday', but Postgres uses interval types that return short names by default, e.g. interval '1 month' returns as '1 mon'.

    I used something like this:

    $str = "mon month monday Mon Monday Month MONTH MON";
    $strMonth = preg_replace('~(mon)([^\w]|$)~i', '$1th$2', $str);
    echo "$str\n$strMonth\n";

    //to output:
    mon month monday Mon Monday Month MONTH MON
    month month monday Month Monday Month MONTH MONth
    akarmenia at gmail dot com
    4 years ago
    [Editor's note: in this case it would be wise to rely on the preg_quote() function instead which was added for this specific purpose]

    If your replacement string has a dollar sign or a backslash. it may turn into a backreference accidentally! This will fix it.

    I want to replace 'text' with '$12345' but this becomes a backreference to $12 (which doesn't exist) and then it prints the remaining '34'. The function down below will return a string that escapes the backreferences.

    OUTPUT:
    string(8) "some 345"
    string(11) "some \12345"
    string(8) "some 345"
    string(11) "some $12345"

    <?php

    $a     = 'some text';

    // Either of these will backreference and fail
    $b1 = '\12345'; // Should be '\\12345' to avoid backreference
    $b2 = '$12345'; // Should be '\$12345' to avoid backreference

    $d = array($b1, $b2);

    foreach (    $d as $b) {
            $result1 = preg_replace('#(text)#', $b, $a); // Fails
            var_dump($result1);
            $result2 = preg_replace('#(text)#', preg_escape_back($b), $a); // Succeeds
            var_dump($result2);
    }

    // Escape backreferences from string for use with regex
    function preg_escape_back($string) {
            // Replace $ with \$ and \ with \\
            $string = preg_replace('#(?<!\\\\)(\\$|\\\\)#', '\\\\$1', $string);
        return     $string;
    }

    ?>
    someuser at dot dot com
    4 years ago
    Replacement of line numbers, with replacement limit per line.

    Solution that worked for me.
    I have a file with tasks listed each starting from number, and only starting number should be removed because forth going text has piles of numbers to be omitted.

    56 Patient A of 46 years suffering ... ...
    57 Newborn of 26 weeks was ...
    58 Jane, having age 18 years recollects onsets of ...
    ...
    587 Patient of 70 years ...

    etc.

    <?php
    // Array obtained from file   
    $array = file($file, true);

    // Decompile array with foreach loop
    foreach($array as $value)
    {
            //    Take away numbers 100-999
        //    Starting from biggest
        //
        //    %            Delimiter
        //    ^            Make match from beginning of line
        //    [0-9]        Range of numbers
        //    {3}        Multiplication of digit range (For tree digit numbers)
        //
            if(preg_match('%^[0-9]{3}%', $value))
        {
                // Re-assing to value its modified copy
                $value = preg_replace('%^[0-9]{3}%', '-HERE WAS XXX NUMBER-', $value, 1);
        }
                   
            // Take away numbers 10-99
            elseif(preg_match('%^[0-9]{2}%', $value)) {
                $value = preg_replace('%^[0-9]{2}%', '-HERE WAS XX NUMBER-', $value, 1);
        }
                   
            // Take away numbers 0-9
            elseif(preg_match('%^[0-9]%', $value)) {
                $value = preg_replace('%^[0-9]%', '-HERE WAS X NUMBER-', $value, 1);
        }
                   
            // Build array back
            $arr[] = array($value);
       
        }
    }
    ?>
    marcin at pixaltic dot com
    7 years ago
    <?php
            //:::replace with anything that you can do with searched string:::
        //Marcin Majchrzak
        //pixaltic.com
       
            $c = "2 4 8";
        echo (    $c); //display:2 4 8

            $cp = "/(\d)\s(\d)\s(\d)/e"; //pattern
            $cr = "'\\3*\\2+\\1='.(('\\3')*('\\2')+('\\1'))"; //replece
            $c = preg_replace($cp, $cr, $c);
        echo (    $c); //display:8*4+2=34
    ?>
    mdrisser at gmail dot com
    7 years ago
    An alternative to the method suggested by sheri is to remember that the regex modifier '$' only looks at the end of the STRING, the example given is a single string consisting of multiple lines.

    Try:
    <?php
    // Following is 1 string containing 3 lines
    $s = "Testing, testing.\r\n"
           . "Another testing line.\r\n"
           . "Testing almost done.";

    echo     preg_replace('/\.\\r\\n/m', '@\r\n', $s);
    ?>

    This results in the string:
    Testing, testing@\r\nAnother testing line@\r\nTesting almost done.
    da_pimp2004_966 at hotmail dot com
    7 years ago
    A simple BB like thing..

    <?php
    function AddBB($var) {
                $search = array(
                        '/\[b\](.*?)\[\/b\]/is',
                        '/\[i\](.*?)\[\/i\]/is',
                        '/\[u\](.*?)\[\/u\]/is',
                        '/\[img\](.*?)\[\/img\]/is',
                        '/\[url\](.*?)\[\/url\]/is',
                        '/\[url\=(.*?)\](.*?)\[\/url\]/is'
                        );

                $replace = array(
                        '<strong>$1</strong>',
                        '<em>$1</em>',
                        '<u>$1</u>',
                        '<img src="$1" />',
                        '<a href="$1">$1</a>',
                        '<a href="$1">$2</a>'
                        );

                $var = preg_replace ($search, $replace, $var);
            return     $var;
    }
    ?>
    7r6ivyeo at mail dot com
    7 years ago
    String to filename:

    <?php
    function string_to_filename($word) {
            $tmp = preg_replace('/^\W+|\W+$/', '', $word); // remove all non-alphanumeric chars at begin & end of string
            $tmp = preg_replace('/\s+/', '_', $tmp); // compress internal whitespace and replace with _
            return strtolower(preg_replace('/\W-/', '', $tmp)); // remove all non-alphanumeric chars except _ and -
    }
    ?>

    Returns a usable & readable filename.
    arie dot benichou at gmail dot com
    7 years ago
    <?php
    //Be carefull with utf-8, even with unicode and utf-8 support enabled, a pretty odd bug occurs depending on your operating system
    $str = "Hi, my name is Arié!<br />";
    echo     preg_replace('#\bArié\b#u', 'Gontran', $str);
    //on windows system, output is "Hi, my name is Gontran<br />"
    //on unix system, output is "Hi, my name is Arié<br />"
    echo preg_replace('#\bArié(|\b)#u', 'Gontran', $str);
    //on windows and unix system, output is "Hi, my name is Gontran<br />"
    jette at nerdgirl dot dk
    7 years ago
    I use this to prevent users from overdoing repeated text. The following function only allows 3 identical characters at a time and also takes care of repetitions with whitespace added.

    This means that 'haaaaaaleluuuujaaaaa' becomes 'haaaleluuujaaa' and 'I am c o o o o o o l' becomes 'I am c o o o l'

    <?php
    //Example of user input
    $str = "aaaaaaaaaaabbccccccccaaaaad d d d   d      d d ddde''''''''''''";

    function     stripRepeat($str) {
          //Do not allow repeated whitespace
          $str = preg_replace("/(\s){2,}/",'$1',$str);
          //Result: aaaaaaaaaaabbccccccccaaaaad d d d d d d ddde''''''''''''

      //Do not allow more than 3 identical characters separated by any whitespace
          $str = preg_replace('{( ?.)\1{4,}}','$1$1$1',$str);
          //Final result: aaabbcccaaad d d ddde'''

          return $str;
    }
    ?>

    To prevent any repetitions of characters, you only need this:

    <?php
    $str     = preg_replace('{(.)\1+}','$1',$str);
    //Result: abcad d d d d d d de'
    ?>
    David
    7 years ago
    Take care when you try to strip whitespaces out of an UTF-8 text. Using something like:

    <?php
    $text     = preg_replace( "{\s+}", ' ', $text );
    ?>

    brokes in my case the letter à which is hex c3a0. But a0 is a whitespace. So use

    <?php
    $text     = preg_replace( "{[ \t]+}", ' ', $text );
    ?>

    to strip all spaces and tabs, or better, use a multibyte function like mb_ereg_replace.
    Michael W
    8 years ago
    For filename tidying I prefer to only ALLOW certain characters rather than converting particular ones that we want to exclude. To this end I use ...

    <?php
      $allowed     = "/[^a-z0-9\\040\\.\\-\\_\\\\]/i";
          preg_replace($allowed,"",$str));
    ?>

    Allows letters a-z, digits, space (\\040), hyphen (\\-), underscore (\\_) and backslash (\\\\), everything else is removed from the string.
    akam AT akameng DOT com
    7 years ago
    <?php                   
    $converted        =
    array(
    //3 of special chars

    '/(;)/ie',
    '/(#)/ie',
    '/(&)/ie',

    //MySQL reserved words!
    //Check mysql website!
    '/(ACTION)/ie', '/(ADD)/ie', '/(ALL)/ie', '/(ALTER)/ie', '/(ANALYZE)/ie', '/(AND)/ie', '/(AS)/ie', '/(ASC)/ie',

    //remaining of special chars
    '/(<)/ie', '/(>)/ie', '/(\.)/ie', '/(,)/ie', '/(\?)/ie', '/(`)/ie', '/(!)/ie', '/(@)/ie', '/(\$)/ie', '/(%)/ie', '/(\^)/ie', '/(\*)/ie', '/(\()/ie', '/(\))/ie', '/(_)/ie', '/(-)/ie', '/(\+)/ie',
    '/(=)/ie', '/(\/)/ie', '/(\|)/ie', '/(\\\)/ie', "/(')/ie", '/(")/ie', '/(:)/'
    );

    $input_text = preg_replace($converted, "UTF_to_Unicode('\\1')", $text);

    function     UTF_to_Unicode($data){

    //return $data;
    }
    ?>
    The above example useful for filtering input data, then saving into mysql database, it's not need tobe decoded again, just use UTF-8 as charset.
    Please Note escaping special chars between delimiter..
    ismith at nojunk dot motorola dot com
    9 years ago
    Be aware that when using the "/u" modifier, if your input text contains any bad UTF-8 code sequences, then preg_replace will return an empty string, regardless of whether there were any matches.

    This is due to the PCRE library returning an error code if the string contains bad UTF-8.
    mike dot hayward at mikeyskona dot co dot uk
    8 years ago
    Hi.
    Not sure if this will be a great help to anyone out there, but thought i'd post just in case.
    I was having an Issue with a project that relied on $_SERVER['REQUEST_URI']. Obviously this wasn't working on IIS.
    (i am using mod_rewrite in apache to call up pages from a database and IIS doesn't set REQUEST_URI). So i knocked up this simple little preg_replace to use the query string set by IIS when redirecting to a PHP error page.

    <?php
    //My little IIS hack :)
    if(!isset($_SERVER['REQUEST_URI'])){
          $_SERVER['REQUEST_URI'] = preg_replace( '/404;([a-zA-Z]+:\/\/)(.*?)\//i', "/" , $_SERVER['QUERY_STRING'] );
    }
    ?>

    Hope this helps someone else out there trying to do the same thing :)
    sternkinder at gmail dot com
    8 years ago
    From what I can see, the problem is, that if you go straight and substitute all 'A's wit 'T's you can't tell for sure which 'T's to substitute with 'A's afterwards. This can be for instance solved by simply replacing all 'A's by another character (for instance '_' or whatever you like), then replacing all 'T's by 'A's, and then replacing all '_'s (or whatever character you chose) by 'A's:

    <?php
    $dna     = "AGTCTGCCCTAG";
    echo     str_replace(array("A","G","C","T","_","-"), array("_","-","G","A","T","C"), $dna); //output will be TCAGACGGGATC
    ?>

    Although I don't know how transliteration in perl works (though I remember that is kind of similar to the UNIX command "tr") I would suggest following function for "switching" single chars:

    <?php
    function switch_chars($subject,$switch_table,$unused_char="_") {
        foreach (     $switch_table as $_1 => $_2 ) {
                $subject = str_replace($_1,$unused_char,$subject);
                $subject = str_replace($_2,$_1,$subject);
                $subject = str_replace($unused_char,$_2,$subject);
        }
        return     $subject;
    }

    echo     switch_chars("AGTCTGCCCTAG", array("A"=>"T","G"=>"C")); //output will be TCAGACGGGATC
    ?>
    rob at ubrio dot us
    8 years ago
    Also worth noting is that you can use array_keys()/array_values() with preg_replace like:

    <?php
    $subs     = array(
          '/\[b\](.+)\[\/b\]/Ui' => '<strong>$1</strong>',
          '/_(.+)_/Ui' => '<em>$1</em>'
          ...
      ...
    );

    $raw_text = '[b]this is bold[/b] and this is _italic!_';

    $bb_text = preg_replace(array_keys($subs), array_values($subs), $raw_text);
    ?>
    mtsoft at mt-soft dot com dot ar
    8 years ago
    This function takes a URL and returns a plain-text version of the page. It uses cURL to retrieve the page and a combination of regular expressions to strip all unwanted whitespace. This function will even strip the text from STYLE and SCRIPT tags, which are ignored by PHP functions such as strip_tags (they strip only the tags, leaving the text in the middle intact).

    Regular expressions were split in 2 stages, to avoid deleting single carriage returns (also matched by \s) but still delete all blank lines and multiple linefeeds or spaces, trimming operations took place in 2 stages.

    <?php
    function webpage2txt($url)
    {
    $user_agent = “Mozilla/4.0 (compatible; MSIE 5.01; Windows NT 5.0)”;

    $ch = curl_init();    // initialize curl handle
    curl_setopt($ch, CURLOPT_URL, $url); // set url to post to
    curl_setopt($ch, CURLOPT_FAILONERROR, 1);              // Fail on errors
    curl_setopt($ch, CURLOPT_FOLLOWLOCATION, 1);    // allow redirects
    curl_setopt($ch, CURLOPT_RETURNTRANSFER,1); // return into a variable
    curl_setopt($ch, CURLOPT_PORT, 80);            //Set the port number
    curl_setopt($ch, CURLOPT_TIMEOUT, 15); // times out after 15s

    curl_setopt($ch, CURLOPT_USERAGENT, $user_agent);

    $document = curl_exec($ch);

    $search = array(’@<script[^>]*?>.*?</script>@si’,  // Strip out javascript
    ‘@<style[^>]*?>.*?</style>@siU’,    // Strip style tags properly
    ‘@<[\/\!]*?[^<>]*?>@si’,            // Strip out HTML tags
    ‘@<![\s\S]*?–[ \t\n\r]*>@’,         // Strip multi-line comments including CDATA
    ‘/\s{2,}/’,

    );

    $text = preg_replace($search, “\n”, html_entity_decode($document));

    $pat[0] = “/^\s+/”;
    $pat[2] = “/\s+\$/”;
    $rep[0] = “”;
    $rep[2] = ” “;

    $text = preg_replace($pat, $rep, trim($text));

    return $text;
    }
    ?>

    Potential uses of this function are extracting keywords from a webpage, counting words and things like that. If you find it useful, drop us a comment and let us know where you used it.
    131 dot php at cloudyks dot org
    8 years ago
    Based on previous comment, i suggest
    ( this function already exist in php 6 )

    <?php
    function unicode_decode($str){
        return     preg_replace(
                '#\\\u([0-9a-f]{4})#e',
                "unicode_value('\\1')",
                $str);
    }

    function     unicode_value($code) {
            $value=hexdec($code);
        if(    $value<0x0080)
            return     chr($value);
        elseif(    $value<0x0800)
            return     chr((($value&0x07c0)>>6)|0xc0)
                .    chr(($value&0x3f)|0x80);
        else
            return     chr((($value&0xf000)>>12)|0xe0)
            .    chr((($value&0x0fc0)>>6)|0x80)
            .    chr(($value&0x3f)|0x80);
    }
    ?>

    [EDIT BY danbrown AT php DOT net:  This function originally written by mrozenoer AT overstream DOT net.]
    lehongviet at gmail dot com
    8 years ago
    I got problem echoing text that contains double-quotes into a text field. As it confuses value option. I use this function below to match and replace each pair of them by smart quotes. The last one will be replaced by a hyphen(-).

    It works for me.

    <?php
    function smart_quotes($text) {
          $pattern = '/"((.)*?)"/i';
          $text = preg_replace($pattern,"“\\1”",stripslashes($text));
          $text = str_replace("\"","-",$text);
          $text = addslashes($text);
      return     $text;
    }
    ?>
    thewolf at pixelcarnage dot com
    12 years ago
    I got sick of trying to replace just a word, so I decided I would write my own string replacement code. When that code because far to big and a little faulty I decided to use a simple preg_replace:

    <?php
    /**
    * Written by Rowan Lewis
    * $search(string), the string to be searched for
    * $replace(string), the string to replace $search
    * $subject(string), the string to be searched in
    */
    function word_replace($search, $replace, $subject) {
        return     preg_replace('/[a-zA-Z]+/e', '\'\0\' == \'' . $search . '\' ? \'' . $replace . '\': \'\0\';', $subject);
    }
    ?>

    I hope that this code helpes someone!
    steven -a-t- acko dot net
    12 years ago
    People using the /e modifier with preg_replace should be aware of the following weird behaviour. It is not a bug per se, but can cause bugs if you don't know it's there.

    The example in the docs for /e suffers from this mistake in fact.

    With /e, the replacement string is a PHP expression. So when you use a backreference in the replacement expression, you need to put the backreference inside quotes, or otherwise it would be interpreted as PHP code. Like the example from the manual for preg_replace:

    preg_replace("/(<\/?)(\w+)([^>]*>)/e",
                 "'\\1'.strtoupper('\\2').'\\3'",
                 $html_body);

    To make this easier, the data in a backreference with /e is run through addslashes() before being inserted in your replacement expression. So if you have the string

    He said: "You're here"

    It would become:

    He said: \"You\'re here\"

    ...and be inserted into the expression.
    However, if you put this inside a set of single quotes, PHP will not strip away all the slashes correctly! Try this:

    print ' He said: \"You\'re here\" ';
    Output: He said: \"You're here\"

    This is because the sequence \" inside single quotes is not recognized as anything special, and it is output literally.

    Using double-quotes to surround the string/backreference will not help either, because inside double-quotes, the sequence \' is not recognized and also output literally. And in fact, if you have any dollar signs in your data, they would be interpreted as PHP variables. So double-quotes are not an option.

    The 'solution' is to manually fix it in your expression. It is easiest to use a separate processing function, and do the replacing there (i.e. use "my_processing_function('\\1')" or something similar as replacement expression, and do the fixing in that function).

    If you surrounded your backreference by single-quotes, the double-quotes are corrupt:
    $text = str_replace('\"', '"', $text);

    People using preg_replace with /e should at least be aware of this.

    I'm not sure how it would be best fixed in preg_replace. Because double-quotes are a really bad idea anyway (due to the variable expansion), I would suggest that preg_replace's auto-escaping is modified to suit the placement of backreferences inside single-quotes (which seemed to be the intention from the start, but was incorrectly applied).
    sreekanth at outsource-online dot net
    4 years ago
    if your intention to code and decode mod_rewrite urls and handle it with php and mysql ,this should work

    to convert to url
    $url = preg_replace('/[^A-Za-z0-9_-]+/', '-', $string);

    And to check in mysql with the url value,use the same expression discounting '-'.
    first replace the url value  with php using preg_replace  and use with mysql REGEXP

    $sql = "select * from table where fieldname_to_check REGEXP '".preg_replace("/-+/",'[^A-Za-z0-9_]+',$url)."'"
    sergei dot garrison at gmail dot com
    6 years ago
    If you want to add simple rich text functionality to HTML input fields, preg_replace can be quite handy.

    For example, if you want users to be able to bold text by typing *text* or italicize it by typing _text_, you can use the following function.

    <?php
    function encode(&$text) {
            $text = preg_replace('/\*([^\*]+)\*/', '<b>\1</b>', $text);
            $text = preg_replace('/_([^_]+)_/', '<i>\1</i>', $text);
        return     $text;
        }
    ?>

    This works for nested tags, too, although it will not fix nesting mistakes.

    To make this function more efficient, you could put the delimiters (* and _, in this case) and their HTML tag equivalents in an array and loop through them.
    gabe at mudbuginfo dot com
    11 years ago
    It is useful to note that the 'limit' parameter, when used with 'pattern' and 'replace' which are arrays, applies to each individual pattern in the patterns array, and not the entire array.
    <?php

    $pattern     = array('/one/', '/two/');
    $replace = array('uno', 'dos');
    $subject = "test one, one two, one two three";

    echo     preg_replace($pattern, $replace, $subject, 1);
    ?>

    If limit were applied to the whole array (which it isn't), it would return:
    test uno, one two, one two three

    However, in reality this will actually return:
    test uno, one dos, one two three
    erik dot stetina at gmail dot com
    4 years ago
    simple function to remove comments from string

    <?php
    function remove_comments( & $string )
    {
          $string = preg_replace("%(#|;|(//)).*%","",$string);
          $string = preg_replace("%/\*(?:(?!\*/).)*\*/%s","",$string); // google for negative lookahead
          return $string;
    }
    ?>

    USAGE:
    <?php
    $config     = file_get_contents("config.cfg");
    print     "before:".$config;
    remove_comments($config);
    print     "after:".$config;
    ?>

    OUTPUT:
    before:
    /*
    *  this is config file
    */
    ; logdir
    LOGDIR ./log/
    // logfile
    LOGFILE main.log
    # loglevel
    LOGLEVEL 3
    after:

    LOGDIR ./log/

    LOGFILE main.log

    LOGLEVEL 3
    ude dot mpco at wotsrabt dot maps-on
    5 years ago
    I find it useful to output HTML form names to the user from time to time while going through the $_GET or $_POST on a user's submission and output keys of the GET or POST array... the only problem being in the name attribute I follow common programming guidelines and have names like the following: eventDate, eventTime, userEmail, etc. Not great to just output to the user-- so I came up with this function. It just adds a space before any uppercase letter in the string.

    <?php
    function caseSwitchToSpaces( $stringVariableName )
    {

    $pattern = '/([A-Z])/';
    $replacement = ' ${1}';

    return     preg_replace( $pattern, $replacement, $stringVariableName );
    }

    //ex.
    echo( caseSwitchToSpaces( "helloWorld" ) );
    ?>

    would output:

    "hello World"

    You could also do title-style casing to it if desired so the first word isn't lowercase.
    Nibbels
    1 year ago
    I have been filtering every userinput with preg_replace since 6 Years now and nothing happened. I am running PHP 5.6.6 and because of historical reasons I still do not use mysqli.
    Now i noticed that this filter [^0-9a-zA-Z_ -|:\.] won't filter anything from a Sleeping-Hack-String like `%' AnD sLeep(3) ANd '1%`:

    preg_replace ( '/[^0-9a-zA-Z_ -|:\.]/', '', "%' AnD sLeep(3) ANd '1%" );

    The reason is, that the fourth Minus has to be escaped!
    Fix: [^0-9a-zA-Z_ \-|:\.]

    I tell you because I did not know this and I am pretty sure btw. maybe in older versions of PHP some did not have to escape this minus. Those hacks did not work in the old days, because formerly I have been testing against this.

    Greetings
    kosalasl at gmail dot com
    4 years ago
    I wrote some useful function to display date format based on date function particular string. preg_replace function really help me to write this tiny code

    <?php
    function mysql2formatDate($strn,$outformat='n/j/Y'){
       
        return     preg_replace("/(\d{4})-(\d{2})-(\d{2})/e","Date('$outformat',strtotime('$0'))",$strn);
    }
    ?>
    tal at ashkenazi dot co dot il
    7 years ago
    after long time of tring get rid of \n\r and <BR> stuff i've came with this...
    (i done some changes in clicklein() function...)

    <?php
            function clickable($url){
                $url                                    =    str_replace("\\r","\r",$url);
                $url                                    =    str_replace("\\n","\n<BR>",$url);
                $url                                    =    str_replace("\\n\\r","\n\r",$url);

                $in=array(
                '`((?:https?|ftp)://\S+[[:alnum:]]/?)`si',
                '`((?<!//)(www\.\S+[[:alnum:]]/?))`si'
                );
                $out=array(
                '<a href="$1"  rel=nofollow>$1</a> ',
                '<a href="http://$1" rel=\'nofollow\'>$1</a>'
                );
            return     preg_replace($in,$out,$url);
        }

    ?>
    halityesil [ at at] globya [ dot dot] net
    7 years ago
    <?PHP

    function strip_tags_attributes($sSource, $aAllowedTags = FALSE, $aDisabledAttributes = FALSE, $aAllowedProperties = 'font|font-size|font-weight|color' . '|text-align|text-decoration|margin|margin-left' . '|margin-top|margin-bottom|margin-right|padding' . '|padding-top|padding-left|padding-right|padding-bottom' . '|width|height'){

       if( !    is_array( $aDisabledAttributes ) ){
              $aDisabledAttributes = array('onabort', 'onactivate', 'onafterprint', 'onafterupdate', 'onbeforeactivate', 'onbeforecopy', 'onbeforecut', 'onbeforedeactivate', 'onbeforeeditfocus', 'onbeforepaste', 'onbeforeprint', 'onbeforeunload', 'onbeforeupdate', 'onblur', 'onbounce', 'oncellchange', 'onchange', 'onclick', 'oncontextmenu', 'oncontrolselect', 'oncopy', 'oncut', 'ondataavaible', 'ondatasetchanged', 'ondatasetcomplete', 'ondblclick', 'ondeactivate', 'ondrag', 'ondragdrop', 'ondragend', 'ondragenter', 'ondragleave', 'ondragover', 'ondragstart', 'ondrop', 'onerror', 'onerrorupdate', 'onfilterupdate', 'onfinish', 'onfocus', 'onfocusin', 'onfocusout', 'onhelp', 'onkeydown', 'onkeypress', 'onkeyup', 'onlayoutcomplete', 'onload', 'onlosecapture', 'onmousedown', 'onmouseenter', 'onmouseleave', 'onmousemove', 'onmoveout', 'onmouseover', 'onmouseup', 'onmousewheel', 'onmove', 'onmoveend', 'onmovestart', 'onpaste', 'onpropertychange', 'onreadystatechange', 'onreset', 'onresize', 'onresizeend', 'onresizestart', 'onrowexit', 'onrowsdelete', 'onrowsinserted', 'onscroll', 'onselect', 'onselectionchange', 'onselectstart', 'onstart', 'onstop', 'onsubmit', 'onunload');
       }
      
           $sSource = stripcslashes( $sSource );
               
           $sSource = strip_tags( $sSource, $aAllowedTags );
           
       if( empty(    $aDisabledAttributes) ){
          return     $sSource;
       }

           $aDisabledAttributes = @ implode('|', $aDisabledAttributes);
           
           $sSource = preg_replace('/<(.*?)>/ie', "'<' . preg_replace(array('/javascript:[^\"\']*/i', '/(" . $aDisabledAttributes . ")[ \\t\\n]*=[ \\t\\n]*[\"\'][^\"\']*[\"\']/i', '/\s+/'), array('', '', ' '), stripslashes('\\1')) . '>'", $sSource );
           $sSource = preg_replace('/\s(' . $aDisabledAttributes . ').*?([\s\>])/', '\\2', $sSource);
               
           $regexp = '@([^;"]+)?(?<!'. $aAllowedProperties .'):(?!\/\/(.+?)\/)((.*?)[^;"]+)(;)?@is';   
           $sSource = preg_replace($regexp, '', $sSource);
           $sSource = preg_replace('@[a-z]*=""@is', '', $sSource);
               
       return     $sSource;
    }

    ?>

    Online resource help skype name : globya

    good luck !
    ulf dot reimers at tesa dot com
    8 years ago
    Hi,

    as I wasn't able to find another way to do this, I wrote a function converting any UTF-8 string into a correct NTFS filename (see http://en.wikipedia.org/wiki/Filename).

    <?php
    function strToNTFSFilename($string)
    {
          $reserved = preg_quote('\/:*?"<>', '/');
      return     preg_replace("/([\\x00-\\x1f{$forbidden}])/e", "_", $string);
    }
    ?>

    It converts all control characters and filename characters which are reserved by Windows ('\/:*?"<>') into an underscore.
    This way you can safely create an NTFS filename out of any UTF-8 string.
    eurosat7 at yahoo dot de
    1 year ago
    If you want to limit multiple occurences of any char in a sequence you might want to use this function.
    <?php
    function limit_char_repeat($string,$maxrepeat){
        return     preg_replace("/(.)\\1{".$maxrepeat.",}/ms",str_repeat('\1',$maxrepeat),$string);
    }
    ?>

    Example:
    <?php
    $string    ="
    ---------------------
    Heeeeeeeeeeeeeeeeeeeello Woooooooooooooooorld!!!!!!!!!!!!!!!!!!!!!!!!
    ===============================================================================================================
    ~~~~~~~~~~~~~~~~ ~ ~ ~
    "    ;
    echo     limit_char_repeat($string,5);
    ?>
    Output:
    -----
    Heeeeello Wooooorld!!!!!
    =====
    ~~~~~ ~ ~ ~
    dhgouveia at gmail dot com
    1 year ago
    if you want to replace only the content of specific div using the ID you can do this :

    <?php
    $id     = "my-id";
    $content = '<div id="my-id">Hello World</div><div  id="other-id"> My World</div>';
    $replacement = "Hello Planet";

    $result  =  preg_replace('/(<div.*?id=\"'.$id.'\"[^>]*>)(.*?)(<\/div>)/i', "$1{$replacement}$3", $content);
      
    echo     $result:
    ?>

    should print :
    <div id="my-id">Hello Planet</div><div  id="other-id"> My World</div>
    jas at rephunter dot net
    2 years ago
    It is recommended that str_replace should be used instead of preg_replace when regex is not needed. In particular, at http://php.net/manual/en/function.str-replace.php it says "If you don't need fancy replacing rules (like regular expressions), you should always use this function instead of preg_replace()."

    While this is usually true, I have found a significant exception to this guideline and benchmarked to show that str_replace is in fact slower in the case when the pattern to be replaced is an array. In particular, when the number of elements in the pattern gets to be around 7, then the preg_replace is faster. Of course this would depend on the specifics of the regex.

    In my case I had pattern arrays with about 40 elements. This becomes far slower with str_replace when there is a simple regex that will do the job.

    Below is the benchmark with some examples of arrays for patterns and an equivalent regex.

    <?php

    /**
    * Title:    Test Harness
    * Author:    **********
    * Date:    27-May-13
    * Project:    *********
    * Purpose:    Test timer comparing str_replace and preg_replace
    *
    * Results:
    *
    * 1. preg_replace is a lot faster!
    * empty loop takes 0.12380504608154 microseconds.
    * Array size: 34
    *  *** str_replace:  6.0163598060608 microseconds.
    *  *** preg_replace: 2.1114869117737 microseconds.
    *
    * 2. str_replace is faster:
    * empty loop takes 0.11837291717529 microseconds.
    * Array size: 3
    *  *** str_replace:  1.7525472640991 microseconds.
    *  *** preg_replace: 2.0717389583588 microseconds.
    *
    * 3. preg_replace is faster:
    * empty loop takes 0.11982989311218 microseconds.
    * Array size: 10
    *  *** str_replace:  2.6692891120911 microseconds.
    *  *** preg_replace: 2.2716360092163 microseconds.
    *
    * 3. about the same: 6 element array is breakeven point to switch to preg_replace
    * empty loop takes 0.12036299705505 microseconds.
    * Array size: 6
    *  *** str_replace:  2.0874700546265 microseconds.
    *  *** preg_replace: 2.1840009689331 microseconds.
    *
    */

    $iterations = 1000000;
    $str1 = 'this is a - test';

    // empty loop
    $begin = microtime(true);
    for (    $i = 0; $i < $iterations; $i++)
    {
    }
    $end = microtime(true);
    $empty_loop_time = $end - $begin;
    echo     "empty loop takes $empty_loop_time microseconds.\n";

    // test1 loop
    // alternate array variations
    //$aStr = array('\r\n','\r','\n','%','.','(',')',':',';','&',"\x07","\x15",'!','\'','"',
    '#','^','*','_','=','+','\\','?','|','<','>','{','}','’','`','~','“','?','$');
    //$aStr = array('\r\n','\r','\n');
    //$aStr = array('0','1','2','3','4','5','6','7','8','9');
    $aStr = array('0','1','2','3','4','5','6');
    $cnt = count($aStr);
    echo     'Array size: ' . $cnt . "\n";
    $begin = microtime(true);
    for (    $i = 0; $i < $iterations; $i++)
    {
            $str2 = str_replace($aStr,'',$str1);
    }
    $end = microtime(true);
    $test1_loop_time = $end - $begin;

    echo     ' *** str_replace:  ';
    $test_time = ($test1_loop_time - $empty_loop_time) * 1000000 / $iterations;
    echo     "$test_time microseconds.\n";

    // test2 loop
    $begin = microtime(true);
    for (    $i = 0; $i < $iterations; $i++)
    {
            $str2 = preg_replace('/[^a-zA-Z\s]/','',$str1);
    }
    $end = microtime(true);
    $test2_loop_time = $end - $begin;

    echo     ' *** preg_replace: ';
    $test_time = ($test2_loop_time - $empty_loop_time) * 1000000 / $iterations;
    echo     "$test_time microseconds.\n";

    ?>
    henke at henke37 dot cjb dot net
    3 years ago
    Warning: not all strings are from a regular language, some are from context free grammars.

    Here is a pair of strings that are impossible to correctly parse with regular expressions:

    a*(b+(c*d)-e)/(f-(g*h)+i)-j

    a[i]b[i]c[/i]d[/i]e[i]f[i]g[/i]h[/i]
    Svoop
    7 years ago
    I have written a short introduction and a colorful cheat sheet for Perl Compatible Regular Expressions (PCRE):

    http://www.bitcetera.com/en/techblog/2008/04/01/regex-in-a-nutshell/
    thegatekeeper1978 at gmail dot com
    1 year ago
    "preg_replace" is able to be exploited with a DOS attack by the user submitting a very long string.  One way I combat this is by using "substr" first to grab the first part of the string.

    $input_string = $_GET['user_input'];

    // If necessary you can log any user attempts to submit a long string
    $string_length = strlen($input_string);
    if($string_lenght > 100){log_func($_SERVER['REMOTE_ADDR'], $string_length, $input_string);}

    $input_string_cut = substr($input_string,0,100);
    $string = preg_replace('/[^a-zA-Z0-9]/', '', $input_string_cut);
    echo($string);
    roscoe-p-coltrane
    6 years ago
    Reading arguments against variables in CSS got me to thinking.

    Process your CSS files in a fashion similar to the following. This particular routine is certainly not the most efficient way, but is what I came up with on the spur of the moment. The prefix token is entirely arbitrary - everything between the leading colon and terminating semicolon is the target. In this way, default values can be put in place, and the constant identifiers simply left as comments, should the stylesheet be used without processing; this would also inhibit your editor from emitting errors about your odd syntax. The declaration pattern at the top assumes something like this:

    /*@css_const
    [
         bgc_a=#ccccee,
            fc_a=#000099,
         bgc_b=#5555cc,
         bgc_c=#eeeeff,
         bgc_d=#599fee
    ]
    */

    ...within the target CSS file.

    Usage like so:

    .Element {
         font-size:10pt;
         color:#000/*fc_a*/;
         background-color:#fff/*bgc_a*/;
    }

    And then...

    <?php
    $dec_pat     = '/^\/\*\@css_const\s+\[(.*)\]\s+\*\//Ums';
    preg_match_all($dec_pat,$css,$m);
    $lhs = array();
    $rhs = array();
    foreach(    $m[1] as &$p) {
            $p = explode(",",$p);
        foreach(    $p as &$q) {
            list(    $k,$v) = explode("=",trim($q));
                $lhs[] = '/(\w+\:).*\/\*' . $k . '\*\/;$/Um';
                $rhs[] = '\1' . $v . ';';
        }
    }
    $css = preg_replace($lhs,$rhs,$css);
    // spit it out or return it; whatever
    ?>

    ...resulting, of course, in:

    .Element {
         font-size:10pt;
         color:#000099;
         background-color:#ccccee;
    }

    Again, efficiency was not the immediate goal, so please don't slay me...
    zzapper
    3 years ago
    yes you can use different pattern delimiters useful when working on an Url

    <?php
    $logo    =preg_replace('#\\.\\./images#','/images',$logo);
    ?>
    heliazolfkhani85 at gmail dot com
    5 months ago
    $pattern='/(09(1|2|3)\d{8})/';
    $string ="n:09128130959 nu: 09371313317 nu:09211313317 n: 09393026988nu:09121572840nnu:09211313317nu:09211313317nu:09121572840";
    $replacements='($1 code $2)';
    echo  preg_replace($pattern, $replacements, $string);
    webmaster at antoinebouchard dot net
    3 years ago
    It may seem useless, but the font tag in Internet Explorer won't recognize compressed hexa values. This is a simple function to uncompress hexa values in the font tag

    <?php
    function colorfix($text) {
        return     preg_replace('/"#([a-f0-9])([a-f0-9])([a-f0-9])"/i', '"#$1$1$2$2$3$3"', $text);
    }
    ?>
    support ~ at ~ mbnad ~ dot ~ com
    4 years ago
    Wrong number of letters in words and how solve this problem and also remove extra spaces in a row:

    <?php
    $message_body     = 'HHHHHEEEEELLLLLOOOOO             IAM COOOOOOOOOOOOOOOOOOOL      !!!!!!!!!!';
    echo     "\n".$message_body."\n";
    $message_body = preg_replace('~(.?)\1{3,}~', '$1', $message_body);
    $message_body = preg_replace('~\s+~', ' ', trim($message_body));
    echo     "\n".$message_body."\n\n";
    ?>
    randall dot reynolds at rightnow dot com
    4 years ago
    The instructions say, use \\\\ (four backslashes) to represent a backslash.  You can shorthand this and use \\\ (three backslashes) to represent a backslash, because of the way the parsers read it.

    It appears the double escaping is required because the string is parsed twice, once by PHP and once by the regular expression generator. Thus it is expected that the PHP parser turns both instances above into \\ (two backslashes) for the PCRE parser.
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