php man page for password_needs_rehash

PASSWORD_NEEDS_REHASH(3)						 1						  PASSWORD_NEEDS_REHASH(3)

password_needs_rehash - Checks if the given hash matches the given options

SYNOPSIS
       boolean password_needs_rehash (string  $hash, integer  $algo, [array  $options])

DESCRIPTION
	This  function checks to see if the supplied hash implements the algorithm and options provided. If not, it is assumed that the hash needs
       to be rehashed.

PARAMETERS
	      o $hash
		- A hash created by password_hash(3).

	      o $algo
		- A password algorithm constant denoting the algorithm to use when hashing the password.

	      o $options
		- An associative array containing options. See the password algorithm constants for documentation on  the  supported  options  for
		each algorithm.

EXAMPLES
       Example #1

	      Usage of password_needs_rehash(3)

	      <?php

	      $password = 'rasmuslerdorf';
	      $hash = '$2y$10$YCFsG6elYca568hBi2pZ0.3LDL5wjgxct1N8w/oLR/jfHsiQwCqTS';

	      // The cost parameter can change over time as hardware improves
	      $options = array('cost' => 11);

	      // Verify stored hash against plain-text password
	      if (password_verify($password, $hash)) {
		  // Check if a newer hashing algorithm is available
		  // or the cost has changed
		  if (password_needs_rehash($hash, PASSWORD_DEFAULT, $options)) {
		      // If so, create a new hash, and replace the old one
		      $newHash = password_hash($password, PASSWORD_DEFAULT, $options);
		  }

		  // Log user in
	      }
	      ?>

RETURN VALUES
	Returns TRUE if the hash should be rehashed to match the given $algo and $options, or FALSE otherwise.

PHP Documentation Group 												  PASSWORD_NEEDS_REHASH(3)