strcspn

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

    strcspn — Find length of initial segment not matching mask

    Description

    strcspn(
        string $string,
        string $characters,
        int $offset = 0,
        ?int $length = null
    ): int

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

    Parameters

    string

    The string to examine.

    characters

    The string containing every disallowed character.

    offset

    The position in string to start searching.

    If offset is given and is non-negative, then strcspn() 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 strcspn() 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 not 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
    8.4.0 Prior to PHP 8.4.0, when characters was the empty string, the search would incorrectly stop at the first null byte in string.
    8.0.0 length is nullable now.

    Examples

    Example #1 strcspn() example

    <?php
    $a     = strcspn('banana', 'a');
    $b = strcspn('banana', 'abcd');
    $c = strcspn('banana', 'z');
    $d = strcspn('abcdhelloabcd', 'a', -9);
    $e = strcspn('abcdhelloabcd', 'a', -9, -5);

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

    The above example will output:

    int(1)
int(0)
int(6)
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 5 notes

    up
    8
    maskedcoder at hotmail dot com
    19 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
    6
    AT-HE (at_he AT hotmai1 DOT com)
    18 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
    2
    legacyprog at routinz dot net
    13 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
    0
    nospam at nospam dot com
    8 years ago
    It might not be clear from the example, that

    strcspn('abcdhelloabcd', 'abcd', -9, -5) == 4

    because it's only evaluating 'hell' which doesn't contain any mask, so returns strlen('hell').
    up
    0
    Anonymous
    15 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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