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    ctype_alnum

    (PHP 4 >= 4.0.4, PHP 5, PHP 7, PHP 8)

    ctype_alnum — Check for alphanumeric character(s)

    Description

    ctype_alnum(mixed $text): bool

    Checks if all of the characters in the provided string, text, are alphanumeric.

    Parameters

    text

    The tested string.

    Note:

    If an int between -128 and 255 inclusive is provided, it is interpreted as the ASCII value of a single character (negative values have 256 added in order to allow characters in the Extended ASCII range). Any other integer is interpreted as a string containing the decimal digits of the integer.

    Warning

    As of PHP 8.1.0, passing a non-string argument is deprecated. In the future, the argument will be interpreted as a string instead of an ASCII codepoint. Depending on the intended behavior, the argument should either be cast to string or an explicit call to chr() should be made.

    Return Values

    Returns true if every character in text is either a letter or a digit, false otherwise. When called with an empty string the result will always be false.

    Examples

    Example #1 A ctype_alnum() example (using the default locale)

    <?php
    $strings     = array('AbCd1zyZ9', 'foo!#$bar');
    foreach (    $strings as $testcase) {
    if (    ctype_alnum($testcase)) {
    echo     "The string $testcase consists of all letters or digits.\n";
    } else {
    echo     "The string $testcase does not consist of all letters or digits.\n";
    }
    }
    ?>

    The above example will output:

    The string AbCd1zyZ9 consists of all letters or digits.
The string foo!#$bar does not consist of all letters or digits.

    See Also

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    User Contributed Notes 4 notes

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    83
    thinice at gmail dot com
    15 years ago
    ctype_alnum() is a godsend for quick and easy username/data filtering when used in conjunction with str_replace().

    Let's say your usernames have dash(-) and underscore(_) allowable and alphanumeric digits as well.

    Instead of a regex you can trade a bit of performance for simplicity:

    <?php
    $sUser     = 'my_username01';
    $aValid = array('-', '_');

    if(!    ctype_alnum(str_replace($aValid, '', $sUser))) {
        echo     'Your username is not properly formatted.';
    }
    ?>
    up
    16
    Anonymous
    11 years ago
    Quicktip: If ctype is not enabled by default on your server, replace ctype_alnum($var) with preg_match('/^[a-zA-Z0-9]+$/', $var).
    up
    3
    marcelocamargo at linuxmail dot org
    8 years ago
    It is also important to note that the behavior of `ctype_alnum` differs according to the operating system. For UNIX-based operating system, if you pass a value that is not a string (or an overloaded object), independently of the value, it will always result in false. However, if we do the same on Windows, using, for example, -1 as literal (a minus and a number greater than 0), we'll have true as result.

    <?php var_dump(ctype_alnum(-1));
    // UNIX: bool(false)
    // Windows: bool(true)
    up
    -7
    Rory
    15 years ago
    Just for the record, Gentoo doesn't include this function by default. You'll have to recompile PHP with the "ctype" USE flag.
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