strcspn

(PHP 4, PHP 5)

strcspnFind length of initial segment not matching mask

Description

int strcspn ( string $subject , string $mask [, int $start [, int $length ]] )

Returns the length of the initial segment of subject which does not contain any of the characters in 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 strcspn(substr($subject, $start, $length), $mask) (see substr for more information).

Parameters

subject

The string to examine.

mask

The string containing every disallowed character.

start

The position in subject to start searching.

If start is given and is non-negative, then strcspn() 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.

Return Values

Returns the length of the initial segment of subject which consists entirely of characters not in mask.

Note:

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

Examples

Example #1 strcspn() example

<?php
$a 
strcspn('abcd',  'apple');
$b strcspn('abcd',  'banana');
$c strcspn('hello''l');
$d strcspn('hello''world');
$e strcspn('abcdhelloabcd''abcd', -9);
$f strcspn('abcdhelloabcd''abcd', -9, -5);

var_dump($a);
var_dump($b);
var_dump($c);
var_dump($d);
var_dump($e);
var_dump($f);
?>

The above example will output:

int(0)
int(0)
int(2)
int(2)
int(5)
int(4)

Notes

Note: This function is binary-safe.

See Also

  • strspn() - Finds the length of the initial segment of a string consisting entirely of characters contained within a given mask.

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User Contributed Notes 4 notes

up
1
maskedcoder at hotmail dot com
9 years ago
useful for finding beginning of quotes and/or tags in a variable containing html. 
    $pos = strcspn($data, '<"\'');
will find the first occurance of either the beginning of a tag, or a double- or single-quoted string.
up
1
AT-HE (at_he AT hotmai1 DOT com)
9 years ago
this function can be used like strspn(), except while that can be used to compare a string with an allowed pattern, this one can be use to compare a string with a FORBIDDEN pattern

so, to know if any forbidden character has a position inside our string, we can use (not tested with backslashes)...

<?php
// LARGE VERSION
$forbidden="\"\\?*:/@|<>";
if (
strlen($filename) != strcspn($filename,$forbidden)) {
    echo
"you cant create a file with that name!";
}

// SHORT VERSION
if (strlen($filename) - strcspn($filename,"\"\\?*:/@|<>")) {
    echo
"i told you, you cant create that file";
}
?>
up
0
legacyprog at routinz dot net
4 years ago
When you use the third parameter remember that the function will return the number of characters it bypassed, which will *not* be the position in your source string.  It's a simple fix to just add your third parameter value to the function result to get the position in the first string where the scan stopped, but I didn't think of it at first.
up
-1
Anonymous
5 years ago
strcspn() can also be thought of as analogous to the following regular expression:
<?php
// where ... represents the mask of characters
preg_match('/[^ ...]/', substr($subject, $start, $length) );
?>
By this analogy, strcspn() can be used in place of some regular expressions to match a pattern without the overhead of a regex engine -- for example, ways to verify if an input string represents a binary value:
<?php
preg_match
('/^[01]+$/i', $subject);
// or...
!preg_match('/[^01]/i', $subject);

// ...or using strcspn()
!strcspn($subject, '01');
?>
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