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    random_bytes

    (PHP 7, PHP 8)

    random_bytes — Get cryptographically secure random bytes

    Description

    random_bytes(int $length): string

    Generates an arbitrary length string of cryptographic random bytes that are suitable for cryptographic use, such as when generating salts, keys or initialization vectors.

    The sources of randomness in the order of priority are as follows:

    • Linux: » getrandom(), /dev/urandom

    • FreeBSD >= 12 (PHP >= 7.3): » getrandom(), /dev/urandom

    • Windows (PHP >= 7.2): » CNG-API

      Windows: » CryptGenRandom

    • macOS (PHP >= 8.2; >= 8.1.9; >= 8.0.22 if CCRandomGenerateBytes is available at compile time): CCRandomGenerateBytes()

      macOS (PHP >= 8.1; >= 8.0.2): arc4random_buf(), /dev/urandom

    • NetBSD >= 7 (PHP >= 7.1; >= 7.0.1): arc4random_buf(), /dev/urandom

    • OpenBSD >= 5.5 (PHP >= 7.1; >= 7.0.1): arc4random_buf(), /dev/urandom

    • DragonflyBSD (PHP >= 8.1): » getrandom(), /dev/urandom

    • Solaris (PHP >= 8.1): » getrandom(), /dev/urandom

    • Any combination of operating system and PHP version not previously mentioned: /dev/urandom
    • If none of the sources are available or they all fail to generate randomness, then a Random\RandomException will be thrown.

    Note: Although this function was added to PHP in PHP 7.0, a » userland implementation is available for PHP 5.2 to 5.6, inclusive.

    Parameters

    length

    The length of the random string that should be returned in bytes; must be 1 or greater.

    Return Values

    A string containing the requested number of cryptographically secure random bytes.

    Errors/Exceptions

    • If an appropriate source of randomness cannot be found, a Random\RandomException will be thrown.
    • If the value of length is less than 1, a ValueError will be thrown.

    Changelog

    Version Description
    8.2.0 In case of a CSPRNG failure, this function will now throw a Random\RandomException. Previously a plain Exception was thrown.

    Examples

    Example #1 random_bytes() example

    <?php
    $bytes     = random_bytes(5);
    var_dump(bin2hex($bytes));
    ?>

    The above example will output something similar to:

    string(10) "385e33f741"

    See Also

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    User Contributed Notes 1 note

    up
    5
    ccbsschucko at gmail dot com
    5 years ago
    <?php
            function str_rand(int $length = 64){ // 64 = 32
                $length = ($length < 4) ? 4 : $length;
            return     bin2hex(random_bytes(($length-($length%2))/2));
        }
       
            var_dump(str_rand());
            // d6199909d0b5fdc22c9db625e4edf0d6da2b113b21878cde19e96f4afe69e714
    ?>
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