(PHP 4, PHP 5, PHP 7)
strspn — Finds the length of the initial segment of a string consisting entirely of characters contained within a given mask.
$subject
, string $mask
[, int $start
[, int $length
]] )
Finds the length of the initial segment of subject
that contains only characters from mask.
If start and length
are omitted, then all of subject will be
examined. If they are included, then the effect will be the same as
calling strspn(substr($subject, $start, $length),
$mask) (see substr
for more information).
The line of code:
<?php
$var = strspn("42 is the answer to the 128th question.", "1234567890");
?>
subject that consists only of characters
contained within "1234567890".
subjectThe string to examine.
maskThe list of allowable characters.
start
The position in subject to
start searching.
If start is given and is non-negative,
then strspn() will begin
examining subject at
the start'th position. For instance, in
the string 'abcdef', the character at
position 0 is 'a', the
character at position 2 is
'c', and so forth.
If start is given and is negative,
then strspn() will begin
examining subject at
the start'th position from the end
of subject.
length
The length of the segment from subject
to examine.
If length is given and is non-negative,
then subject will be examined
for length characters after the starting
position.
If length is given and is negative,
then subject will be examined from the
starting position up to length
characters from the end of subject.
Returns the length of the initial segment of subject
which consists entirely of characters in mask.
Note:
When a
startparameter is set, the returned length is counted starting from this position, not from the beginning ofsubject.
Example #1 strspn() example
<?php
// subject does not start with any characters from mask
var_dump(strspn("foo", "o"));
// examine two characters from subject starting at offset 1
var_dump(strspn("foo", "o", 1, 2));
// examine one character from subject starting at offset 1
var_dump(strspn("foo", "o", 1, 1));
?>
The above example will output:
int(0) int(2) int(1)
Note: This function is binary-safe.
you can use this function with strlen to check illegal characters, string lenght must be the same than strspn (characters from my string contained in another)
<?php
$digits='0123456789';
if (strlen($phone) != strspn($phone,$digits))
echo "illegal characters";
?>
It took me some time to understand the way this function works…
I’ve compiled my own explanation with my own words that is more understandable for me personally than the official one or those that can be found in different tutorials on the web.
Perhaps, it will save someone several minutes…
<?php
strspn(string $haystack, string $char_list [, int $start [, int $length]])
?>
The way it works:
- searches for a segment of $haystack that consists entirely from supplied through the second argument chars
- $haystack must start from one of the chars supplied through $char_list, otherwise the function will find nothing
- as soon as the function encounters a char that was not mentioned in $chars it understands that the segment is over and stops (it doesn’t search for the second, third and so on segments)
- finally, it measures the segment’s length and return it (i.e. length)
In other words it finds a span (only the first one) in the string that consists entirely form chars supplied in $chars_list and returns its length
This function is significantly faster for checking illegal characters than the equivalent preg_match() method.
Quick way to check if a string consists entirely of characters within the mask is to compare strspn with strlen eg:
<?php
$path = $_SERVER['PATH_INFO'];
if (strspn($path,'/') == strlen($path)) {
//PATH_INFO is empty
}
?>
The second parameter is a set of allowed characters.
strspn will return an zero-based index of a first non-allowed character.
very dificult to get from the definition directly, while i search for that,i came to know that
strspn() will tell you the length of a string consisting entirely of the set of characters in accept set. That is, it starts walking down str until it finds a character that is not in the set (that is, a character that is not to be accepted), and returns the length of the string so far.
and
strcspn() works much the same way, except that it walks down str until it finds a character in the reject set (that is, a character that is to be rejected.) It then returns the length of the string so far.
<?php
$acceptSet = "aeiou";
$rejectSet = "y";
$str1 ="a banana";
$str2 ="the bolivian navy on manuvers in the south pacific";
echo $n = strspn($str1,$acceptSet);// $n == 1, just "a"
echo $n = strcspn($str2,$rejectSet);// n = 16, "the bolivian nav"
?>
hope this example will help in understanding the concept of strspn() and strcspn().
