openssl_random_pseudo_bytes(3) php man page | unix.com

OPENSSL_RANDOM_PSEUDO_BYTES(3)						 1					    OPENSSL_RANDOM_PSEUDO_BYTES(3)

openssl_random_pseudo_bytes - Generate a pseudo-random string of bytes

SYNOPSIS
       string openssl_random_pseudo_bytes (int	$length, [bool	&$crypto_strong])

DESCRIPTION
	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
	      o $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.

	      o $crypto_strong
		-  If  passed  into  the  function,  this  will  hold a boolean 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(3) 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: 0
	      string(0) ""
	      NULL

	      Lengths: Bytes: 0 and Hex: 0
	      string(0) ""
	      NULL

	      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(3), bin2hex(3), crypt(3), mt_rand(3), uniqid(3).
PHP Documentation Group 											    OPENSSL_RANDOM_PSEUDO_BYTES(3)