(PHP 5 >= 5.3.0, PHP 7)

openssl_random_pseudo_bytesGenerate a pseudo-random string of bytes


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.



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.


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.


Example #1 openssl_random_pseudo_bytes() example

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;
    echo PHP_EOL;

The above example will output something similar to:

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

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

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

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

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

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