Php/docs/function.openssl-random-pseudo-bytes

• PHP Manual
• OpenSSL Functions
• Generate a pseudo-random string of bytes

openssl_random_pseudo_bytes

(PHP 5 >= 5.3.0, PHP 7)

openssl_random_pseudo_bytes — Generate a pseudo-random string of bytes

Description

openssl_random_pseudo_bytes ( int $length [, bool &$crypto_strong ] ) : string|false

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 crypto_strong 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. PHP will try to cast this parameter to a non-null integer to use it.

crypto_strong

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 on success, or FALSE on failure.

Examples

Example #1 openssl_random_pseudo_bytes() example

<?phpfor ($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)

See Also

• random_bytes() - Generates cryptographically secure pseudo-random bytes
• bin2hex() - Convert binary data into hexadecimal representation
• crypt() - One-way string hashing
• mt_rand() - Generate a random value via the Mersenne Twister Random Number Generator
• uniqid() - Generate a unique ID