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strspn

(PHP 4, PHP 5, PHP 7, PHP 8)

strspn Finds the length of the initial segment of a string consisting entirely of characters contained within a given mask

Description

strspn ( string $string , string $characters , int $offset = 0 , int|null $length = null ) : int

Finds the length of the initial segment of string that contains only characters from characters.

If offset and length are omitted, then all of string 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");
?>
will assign 2 to $var, because the string "42" is the initial segment of string that consists only of characters contained within "1234567890".

Parameters

string

The string to examine.

characters

The list of allowable characters.

offset

The position in string to start searching.

If offset is given and is non-negative, then strspn() will begin examining string at the offset'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 offset is given and is negative, then strspn() will begin examining string at the offset'th position from the end of string.

length

The length of the segment from string to examine.

If length is given and is non-negative, then string will be examined for length characters after the starting position.

If length is given and is negative, then string will be examined from the starting position up to length characters from the end of string.

Return Values

Returns the length of the initial segment of string which consists entirely of characters in characters.

Note:

When a offset parameter is set, the returned length is counted starting from this position, not from the beginning of string.

Changelog

Version Description
8.0.0 length is nullable now.

Examples

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"12));

// examine one character from subject starting at offset 1
var_dump(strspn("foo""o"11));
?>

The above example will output:

int(0)
int(2)
int(1)

Notes

Note: This function is binary-safe.

See Also

  • strcspn() - Find length of initial segment not matching mask

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User Contributed Notes 9 notes

up
20
AT-HE (at_he.hotmail)
10 years ago
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";

?>
up
19
barry dot balkowski at gmail dot com
12 years ago
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
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8
B Crawford
13 years ago
This function is significantly faster for checking illegal characters than the equivalent preg_match() method.
up
4
bob at example dot com
8 years ago
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
}
?>
up
5
mrsohailkhan at gmail dot com
9 years ago
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().
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1
nino dot skopac at gmail dot com
2 years ago
strspon and preg_match seem to be equally fast for validating numbers:

<?php

$testValInvalid
= 'foobar123^^';
$testValValid = '12346';
$allowedChars = '1234567890';

$t1 = microtime(true);
for (
$i = 0; $i < 1000000; $i++) {
   
assert(strspn($testValInvalid, $allowedChars) != strlen($testValInvalid));
   
assert(strspn($testValValid, $allowedChars) == strlen($testValValid));
}
print
'Time taken for strspon: ' . (microtime(true) - $t1);
print
PHP_EOL;

$t1 = microtime(true);
for (
$i = 0; $i < 1000000; $i++) {
   
assert(preg_match('/^[0-9]+$/', $testValInvalid) === 0);
   
assert(preg_match('/^[0-9]+$/', $testValValid));
}

print
'Time taken for preg_match: ' . (microtime(true) - $t1);
print
PHP_EOL;

/**
nino-mcb:hosp_web ninoskopac$ php test.php
Time taken for strspon: 3.24165391922
Time taken for preg_match: 3.1820080280304
nino-mcb:hosp_web ninoskopac$ php test.php
Time taken for strspon: 3.1806418895721
Time taken for preg_match: 3.2244551181793
*/
?>
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2
Dmitry Mazur
11 years ago
The second parameter is a set of allowed characters.
strspn will return an zero-based index of a first non-allowed character.
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1
lincoln dot mahmud at gmail dot com
5 months ago
Get Group match letter

<?php

$s
= 'aaabbbcceeffaaeeeaaabbzmmm';

function
groupby( $s ){
    static
$a = [];
    static
$i = 0;
   
   
$o = strspn( $s, $s[$i], $i);
   
$a[ $i ] = [  $s[$i] => $o ];
   
$i += $o;
   
    if(
$i < strlen($s) ) {
       
groupby($s);
    }

    return
$a;
}

print_r(groupby($s));

?>
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-3
ayaou dot mohammed at gmail dot com
1 year ago
This function doesn't  work with non ASCII characters

Exemple:

<?php

$subject
= "Comment ça va ma chérie";
$mask = "éèçà";

echo
strspn($subject,$mask); // Echo 0

?>

See, we expected  1 but 0 was the correct result
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