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 $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($string, $offset, $length), $characters) (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", 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)

    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 8 notes

    up
    25
    barry dot balkowski at gmail dot com
    16 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
    up
    22
    AT-HE (at_he.hotmail)
    13 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
    10
    B Crawford
    17 years ago
    This function is significantly faster for checking illegal characters than the equivalent preg_match() method.
    up
    7
    mrsohailkhan at gmail dot com
    13 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().
    up
    5
    Dmitry Mazur
    15 years ago
    The second parameter is a set of allowed characters.
    strspn will return an zero-based index of a first non-allowed character.
    up
    3
    bob at example dot com
    12 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
    1
    lincoln dot mahmud at gmail dot com
    4 years 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));

    ?>
    up
    -1
    nino dot skopac at gmail dot com
    6 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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