PHP Manual: Generate a pseudo-random string of bytes

Description

string openssl_random_pseudo_bytes(int $length, bool &$strong_result = null)

Generates a string of pseudo-random bytes, with the number of bytes determined by the length parameter.

It also indicates if a cryptographically strong algorithm was used to produce the pseudo-random bytes, and does this via the optional strong_result parameter. It's rare for this to be false, but some systems may be broken or old.

Parameters

length: The length of the desired string of bytes. Must be a positive integer less than or equal to 2147483647. PHP will try to cast this parameter to a non-null integer to use it.
strong_result: If passed into the function, this will hold a bool value that determines if the algorithm used was "cryptographically strong", e.g., safe for usage with GPG, passwords, etc. true if it did, otherwise false

Return Values

Returns the generated string of bytes.

Errors/Exceptions

openssl_random_pseudo_bytes throws an Exception on failure.

Changelog

Version	Description
8.0.0	`strong_result` is nullable now.
7.4.0	The function no longer returns `false` on failure, but throws an Exception instead.

Examples

Example #1 openssl_random_pseudo_bytes example

<?php
for ($i = 1; $i <= 4; $i++) {
    $bytes = openssl_random_pseudo_bytes($i, $cstrong);
    $hex   = bin2hex($bytes);

    echo "Lengths: Bytes: $i and Hex: " . strlen($hex) . PHP_EOL;
    var_dump($hex);
    var_dump($cstrong);
    echo PHP_EOL;
}
?>

The above example will output something similar to:

Lengths: Bytes: 1 and Hex: 2
string(2) "42"
bool(true)

Lengths: Bytes: 2 and Hex: 4
string(4) "dc6e"
bool(true)

Lengths: Bytes: 3 and Hex: 6
string(6) "288591"
bool(true)

Lengths: Bytes: 4 and Hex: 8
string(8) "ab86d144"
bool(true)

openssl_random_pseudo_bytes