preg_split

(PHP 4, PHP 5, PHP 7)

preg_split — Split string by a regular expression

Description

array preg_split ( string $pattern , string $subject [, int $limit = -1 [, int $flags = 0 ]] )

Split the given string by a regular expression.

Parameters

pattern

The pattern to search for, as a string.

subject

The input string.

limit

If specified, then only substrings up to limit are returned with the rest of the string being placed in the last substring. A limit of -1, 0 or NULL means "no limit" and, as is standard across PHP, you can use NULL to skip to the flags parameter.

flags

flags can be any combination of the following flags (combined with the | bitwise operator):

PREG_SPLIT_NO_EMPTY: If this flag is set, only non-empty pieces will be returned by preg_split().
PREG_SPLIT_DELIM_CAPTURE: If this flag is set, parenthesized expression in the delimiter pattern will be captured and returned as well.
PREG_SPLIT_OFFSET_CAPTURE: If this flag is set, for every occurring match the appendant string offset will also be returned. Note that this changes the return value in an array where every element is an array consisting of the matched string at offset 0 and its string offset into subject at offset 1.

Return Values

Returns an array containing substrings of subject split along boundaries matched by pattern.

Examples

Example #1 preg_split() example : Get the parts of a search string


<?php
// split the phrase by any number of commas or space characters,
// which include " ", \r, \t, \n and \f
$keywords = preg_split("/[\s,]+/", "hypertext language, programming");
print_r($keywords);
?>

The above example will output:

Array
(
    [0] => hypertext
    [1] => language
    [2] => programming
)

Example #2 Splitting a string into component characters


<?php
$str = 'string';
$chars = preg_split('//', $str, -1, PREG_SPLIT_NO_EMPTY);
print_r($chars);
?>

The above example will output:

Array
(
    [0] => s
    [1] => t
    [2] => r
    [3] => i
    [4] => n
    [5] => g
)

Example #3 Splitting a string into matches and their offsets


<?php
$str = 'hypertext language programming';
$chars = preg_split('/ /', $str, -1, PREG_SPLIT_OFFSET_CAPTURE);
print_r($chars);
?>

The above example will output:

Array
(
    [0] => Array
        (
            [0] => hypertext
            [1] => 0
        )

    [1] => Array
        (
            [0] => language
            [1] => 10
        )

    [2] => Array
        (
            [0] => programming
            [1] => 19
        )

)

Notes

Tip

If you don't need the power of regular expressions, you can choose faster (albeit simpler) alternatives like explode() or str_split().

Tip

If matching fails, an array with a single element containing the input string will be returned.

User Contributed Notes

markac

1 year ago


Split string into words.

<?php
$string = 'This - is a, very dirty "string" :-)';

// split into words
$wordlist = preg_split('/\W/', $string, 0, PREG_SPLIT_NO_EMPTY);

// returns only words that have minimum 2 chars
$wordlist = array_filter($wordlist, function($val) {
  return strlen($val) >= 2;
});

// print
var_dump($wordlist);
?>

Result:

array (size=5)
  0 => string 'This' (length=4)
  1 => string 'is' (length=2)
  3 => string 'very' (length=4)
  4 => string 'dirty' (length=5)
  5 => string 'string' (length=6)

jan dot sochor at icebolt dot info

6 years ago


Sometimes PREG_SPLIT_DELIM_CAPTURE does strange results.

<?php
$content = '<strong>Lorem ipsum dolor</strong> sit <img src="test.png" />amet <span class="test" style="color:red">consec<i>tet</i>uer</span>.';
$chars = preg_split('/<[^>]*[^\/]>/i', $content, -1, PREG_SPLIT_NO_EMPTY | PREG_SPLIT_DELIM_CAPTURE);
print_r($chars);
?>
Produces:
Array
(
    [0] => Lorem ipsum dolor
    [1] =>  sit <img src="test.png" />amet 
    [2] => consec
    [3] => tet
    [4] => uer
)

So that the delimiter patterns are missing. If you wanna get these patters remember to use parentheses.

<?php
$chars = preg_split('/(<[^>]*[^\/]>)/i', $content, -1, PREG_SPLIT_NO_EMPTY | PREG_SPLIT_DELIM_CAPTURE);
print_r($chars); //parentheses added
?>
Produces:
Array
(
    [0] => <strong>
    [1] => Lorem ipsum dolor
    [2] => </strong>
    [3] =>  sit <img src="test.png" />amet 
    [4] => <span class="test" style="color:red">
    [5] => consec
    [6] => <i>
    [7] => tet
    [8] => </i>
    [9] => uer
    [10] => </span>
    [11] => .
)

eric at clarinova dot com

4 years ago


Here is another way to split a CamelCase string, which is a simpler expression than the one using lookaheads and lookbehinds: 

preg_split('/([[:upper:]][[:lower:]]+)/', $last, null, PREG_SPLIT_DELIM_CAPTURE|PREG_SPLIT_NO_EMPTY)

It makes the entire CamelCased word the delimiter, then returns the delimiters (PREG_SPLIT_DELIM_CAPTURE) and omits the empty values between the delimiters (PREG_SPLIT_NO_EMPTY)

buzoganylaszlo at yahoo dot com

6 years ago


Extending m.timmermans's solution, you can use the following code as a search expression parser:

<?php
$search_expression = "apple bear \"Tom Cruise\" or 'Mickey Mouse' another word";
$words = preg_split("/[\s,]*\\\"([^\\\"]+)\\\"[\s,]*|" . "[\s,]*'([^']+)'[\s,]*|" . "[\s,]+/", $search_expression, 0, PREG_SPLIT_NO_EMPTY | PREG_SPLIT_DELIM_CAPTURE);
print_r($words);
?>

The result will be:
Array
(
    [0] => apple
    [1] => bear
    [2] => Tom Cruise
    [3] => or
    [4] => Mickey Mouse
    [5] => another
    [6] => word
)

1. Accepted delimiters: white spaces (space, tab, new line etc.) and commas.

2. You can use either simple (') or double (") quotes for expressions which contains more than one word.

jetsoft at iinet.net.au

11 years ago


To clarify the "limit" parameter and the PREG_SPLIT_DELIM_CAPTURE option,



<?php

$preg_split('(/ /)', '1 2 3 4 5 6 7 8', 4 ,PREG_SPLIT_DELIM_CAPTURE );

?>



returns:



('1', ' ', '2', ' ' , '3', ' ', '4 5 6 7 8')



So you actually get 7 array items not 4

6 years ago


Spacing out your CamelCase using preg_replace:

<?php

function spacify($camel, $glue = ' ') {
    return preg_replace( '/([a-z0-9])([A-Z])/', "$1$glue$2", $camel );
}

echo spacify('CamelCaseWords'), "\n"; // 'Camel Case Words'
echo spacify('camelCaseWords'), "\n"; // 'camel Case Words'

?>

Daniel Schroeder

5 years ago


If you want to split by a char, but want to ignore that char in case it is escaped, use a lookbehind assertion.



In this example a string will be split by ":" but "\:" will be ignored:



<?php

$string='a:b:c\:d';

$array=preg_split('#(?<!\\\)\:#',$string);

print_r($array);

?>



Results into:



Array

(

    [0] => a

    [1] => b

    [2] => c\:d

)

php at dmi dot me dot uk

6 years ago


To split a camel-cased string using preg_split() with lookaheads and lookbehinds:

<?php
function splitCamelCase($str) {
  return preg_split('/(?<=\\w)(?=[A-Z])/', $str);
}
?>

csaba at alum dot mit dot edu

7 years ago


If the task is too complicated for preg_split, preg_match_all might come in handy, since preg_split is essentially a special case.

I wanted to split a string on a certain character (asterisk), but only if it wasn't escaped (by a preceding backslash).  Thus, I should ensure an even number of backslashes before any asterisk meant as a splitter.  Look-behind in a regular expression wouldn't work since the length of the preceding backslash sequence can't be fixed.  So I turned to preg_match_all:

<?php
// split a string at unescaped asterisks
// where backslash is the escape character
$splitter = "/\\*((?:[^\\\\*]|\\\\.)*)/";
preg_match_all($splitter, "*$string", $aPieces, PREG_PATTERN_ORDER);
$aPieces = $aPieces[1];

// $aPieces now contains the exploded string
// and unescaping can be safely done on each piece
foreach ($aPieces as $idx=>$piece)
  $aPieces[$idx] = preg_replace("/\\\\(.)/s", "$1", $piece);
?>

david dot binovec at gmail dot com

4 years ago


Limit = 1 may be confusing. The important thing is that in case of limit equals to 1 will produce only ONE substring. Ergo the only one substring will be the first one as well as the last one. Tnat the rest of the string (after the first delimiter) will be placed to the last substring. But last is the first and only one.

<?php

$output = $preg_split('(/ /)', '1 2 3 4 5 6 7 8', 1); 

echo $output[0] //will return whole string!;

$output = $preg_split('(/ /)', '1 2 3 4 5 6 7 8', 2); 

echo $output[0] //will return 1;
echo $output[1] //will return '2 3 4 5 6 7 8';

?>

canadian dot in dot exile at gmail dot com

5 months ago


This regular expression will split a long string of words into an array of sub-strings, of some maximum length, but only on word-boundries.

I use the reg-ex with preg_match_all(); but, I'm posting this example here (on the page for preg_split()) because that's where I looked when I wanted to find a way to do this.

Hope it saves someone some time.

<?php
// example of a long string of words
$long_string = 'Your IP Address will be logged with the submitted note and made public on the PHP manual user notes mailing list. The IP address is logged as part of the notes moderation process, and won\'t be shown within the PHP manual itself.';

// "word-wrap" at, for example, 60 characters or less
$max_len = 60;

// this regular expression will split $long_string on any sub-string of
// 1-or-more non-word characters (spaces or punctuation)
if(preg_match_all("/.{1,{$max_len}}(?=\W+)/", $long_string, $lines) !== False) {

    // $lines now contains an array of sub-strings, each will be approx.
    // $max_len characters - depending on where the last word ended and
    // the number of 'non-word' characters found after the last word
    for ($i=0; $i < count($lines[0]); $i++) {
        echo "[$i] {$lines[0][$i]}\n";
    }
}
?>

Steve

11 years ago


preg_split() behaves differently from perl's split() if the string ends with a delimiter. This perl snippet will print 5:



my @a = split(/ /, "a b c d e ");

print scalar @a;



The corresponding php code prints 6:



<?php print count(preg_split("/ /", "a b c d e ")); ?>



This is not necessarily a bug (nowhere does the documentation say that preg_split() behaves the same as perl's split()) but it might surprise perl programmers.

PhoneixSegovia at gmail dot com

5 years ago


You must be caution when using lookbehind to a variable match.
For example:
'/(?<!\\\)\r?\n)/'
 to match a new line when not \ is before it don't go as spected as it match \r as the lookbehind (becouse isn't a \) and is optional before \n.

You must use this for example:
'/((?<!\\\|\r)\n)|((?<!\\\)\r\n)/'
That match a alone \n (not preceded by \r or \) or a \r\n not preceded by a \.

Miller

2 years ago


This is a function to truncate a string of text while preserving the whitespace (for instance, getting an excerpt from an article while maintaining newlines). It will not jive well with HTML, of course.

<?php
/**
 * Truncates a string of text by word count
 * @param string $text The text to truncate
 * @param int $max_words The maximum number of words
 * @return string The truncated text
 */
function limit_words ($text, $max_words) {
    $split = preg_split('/(\s+)/', $text, -1, PREG_SPLIT_DELIM_CAPTURE);
    $truncated = '';
    for ($i = 0; $i < min(count($split), $max_words*2); $i += 2) {
        $truncated .= $split[$i].$split[$i+1];
    }
    return trim($truncated);
}
?>

nesbert at gmail dot com

6 years ago


Hope this helps someone...



<?php

/**

 * Split a string into groups of words with a line no longer than $max

 * characters.

 *

 * @param string $string

 * @param integer $max

 * @return array

 **/

function split_words($string, $max = 1)

{

    $words = preg_split('/\s/', $string);

    $lines = array();

    $line = '';

    

    foreach ($words as $k => $word) {

        $length = strlen($line . ' ' . $word);

        if ($length <= $max) {

            $line .= ' ' . $word;

        } else if ($length > $max) {

            if (!empty($line)) $lines[] = trim($line);

            $line = $word;

        } else {

            $lines[] = trim($line) . ' ' . $word;

            $line = '';

        } 

    }

    $lines[] = ($line = trim($line)) ? $line : $word;



    return $lines;

}

?>

Peter -the pete- de Pijd

6 years ago


If you want to use something like explode(PHP_EOL, $string) but for all combinations of \r and \n, try this one:



<?php

$text = "A\nB\rC\r\nD\r\rE\n\nF";

$texts = preg_split("/((\r(?!\n))|((?<!\r)\n)|(\r\n))/", $text);

?>



result:

array("A", "B", "C", "D", "", "E", "", "F");

kenorb at gmail dot com

6 years ago


If you need convert function arguments without default default values and references, you can try this code:

<?php
    $func_args = '$node, $op, $a3 = NULL, $form = array(), $a4 = NULL'
    $call_arg = preg_match_all('@(?<func_arg>\$[^,= ]+)@i', $func_args, $matches);
    $call_arg = implode(',', $matches['func_arg']);
?>
Result: string = "$node,$op,$a3,$form,$a4"

anajilly

7 years ago


<?php

$s = '<p>bleh blah</p><p style="one">one two three</p>';



$htmlbits = preg_split('/(<p( style="[-:a-z0-9 ]+")?>|<\/p>)/i', $s, -1, PREG_SPLIT_DELIM_CAPTURE);



print_r($htmlbits);

?>



Array

(

    [0] =>

    [1] => <p>

    [2] => bleh blah

    [3] => </p>

    [4] =>

    [5] => <p style="one">

    [6] =>  style="one"

    [7] => one two three

    [8] => </p>

    [9] =>

)



two interesting bits:



1. When using PREG_SPLIT_DELIM_CAPTURE, if you use more than one pair of parentheses, the result array can have members representing all pairs.  See array indexes 5 and 6 to see two adjacent delimiter results in which the second is a subset match of the first.



2. If a parenthesised sub-expression is made optional by a following question mark (ex: '/abc (optional subregex)?/') some split delimiters may be captured in the result while others are not.  See array indexes 1 and 2 to see an instance where the overall match succeeded and returned a delimiter while the optional sub-expression '( style="[-:a-z0-9 ]+")?' did not match, and did not return a delimiter.  This means it's possible to have a result with an unpredictable number of delimiters in the result array.



This second aspect is true irrespective of the number of pairs of parentheses in the regex.  This means: in a regular expression with a single optional parenthesised sub-expression, the overall expression can match without generating a corresponding delimiter in the result.

w o z 2 2 a t y a h o o d o t c o m

4 years ago


PREG_SPLIT_OFFSET_CAPTURE should be maintained for UTF-8 characters, because it produces wrong results as if it is using strlen() internally, instead of using mb_strlen(), which is the right one...

anton at zebooka dot com

2 years ago


A not good code in example regexp.
It should be written 
preg_split("/[\\s,]+", ...
because there is no special symbol \s (like \n for example) and we need to pass exactly \s, not symbol that \s may represent.
So we need to escape backslash with backslash

$a = "/[\\s,+]/";
echo $a;
php> /[\s,+]/

preg_split

Description

Parameters

Return Values

Examples

Notes

See Also

User Contributed Notes