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# PHP password_needs_rehash() Function [PHP Password Hashing Algorithm](#) The password_needs_rehash() function is used to check if a hash value matches the specified options. PHP Version Requirement: PHP 5 >= 5.5.0, PHP 7 ### Syntax bool password_needs_rehash ( string $hash , int $algo [, array $options ] ) Parameter Explanation: * hash: A hash value created by password_hash(). * algo: A password algorithm constant used to indicate the algorithm when hashing passwords. * options: An associative array containing options. Currently, two options are supported: salt, the salt (interference string) added when hashing passwords, and cost, which specifies the number of recursive layers of the algorithm. Examples of these values can be found on the crypt() page. If omitted, a random salt and the default cost will be used. ### Return Value This function checks whether the specified hash value implements the provided algorithm and options. If not, the hash value needs to be regenerated. ### Example ## password_needs_rehash() Usage 11); // Verify the stored hash against the plaintext password if(password_verify($password, $hash)){// Check if there is a newer available hash algorithm// Or if the cost has changed if(password_needs_rehash($hash, PASSWORD_DEFAULT, $options)){// If so, create a new hash and replace the old one$newHash = password_hash($password, PASSWORD_DEFAULT, $options); }// Log the user in}?>
[PHP Password Hashing Algorithm](#)