PHP 5.6.16 is available


(PHP 5 >= 5.5.0)

password_needs_rehashVérifie que le hachage fourni est conforme à l'algorithme et aux options spécifiées


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

Cette fonction vérifie que le hachage fourni correspond à l'algorithme et aux options spécifiées. Si ce n'est pas le cas, le hachage devrait être re-généré.

Liste de paramètres


Un hachage créé par la fonction password_hash().


Une constantes de l'algorithme de mot de passe représentant l'algorithme à utiliser lors du hachage du mot de passe.


Un tableau associatif contenant les options. Voir aussi les constantes de l'algorithme de mot de passe pour une documentation sur les options supportées pour chaque algorithme.


Exemple #1 Usage de password_needs_rehash()


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

// Le paramètre cost peut évoluer avec le temps en fonction des améliorations 
// matérielles.
$options = array('cost' => 11);

// Vérifions d'abord que le mot de passe correspond au hachage stocké
if (password_verify($password$hash)) {
// Le hachage correspond, on vérifie au cas où un nouvel algorithme de hachage
    // serait disponible ou si le coût a été changé
if (password_needs_rehash($hashPASSWORD_DEFAULT$options)) {
// On crée un nouveau hachage afin de mettre à jour l'ancien
$newHash password_hash($passwordPASSWORD_DEFAULT$options);

// On connecte l'utilisateur

Valeurs de retour

Retourne TRUE si le hachage doit être re-généré pour correspondre aux paramètres algo et options fournis, ou FALSE sinon.

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User Contributed Notes 4 notes

admin at torntech dot com
1 year ago
Some other use-cases for the password_needs_rehash function is when you have specified using the PASSWORD_DEFAULT algorithm for password_hash.
As mentioned on the Password Hashing Predefined Constants and password_hash pages, the algorithm used by PASSWORD_DEFAULT is subject to change as different versions of PHP are released.
Additionally password_needs_rehash would be used if you have changed the optional cost or static salt (DO NOT USE A STATIC SALT) requirements of your password_hash options.

Full example:


= [
'options' => ['cost' => 11],
'hash' => null

$password = 'rasmuslerdorf';

//stored hash of password
$oldHash = '$2y$07$BCryptRequires22Chrcte/VlQH0piJtjXl.0t1XkA8pw9dMXTpOq';

//verify stored hash against plain-text password
if (true === password_verify($password, $oldHash)) {
//verify legacy password to new password_hash options
if (true === password_needs_rehash($oldHash, $new['algo'], $new['options'])) {
//rehash/store plain-text password using new hash
$newHash = password_hash($password, $new['algo'], $new['options']);

The above example will output something similar to:
nick at nickstallman dot net
2 years ago
ydroneaud this would be used on a login page, not at any other time.

So if you have a site with MD5 passwords for example, and wish to upgrade to SHA256 for additional security you would put this check in the login script.

This function will take a user's hash and say if it is SHA256, if it isn't then you can take the user's password which you still have as plaintext and rehash it as SHA256.

This lets you gradually update the hashes in your database without disrupting any features or resetting passwords.
php dot net at muer dot nl
1 year ago
nick, this function cannot check if a string is a MD5 or SHA1 hash. It can only tell you if a password, hashed using the password_hash function, needs to be put through the hashing function again to keep up to date with the new defaults.

The only time you can use this function is when your user logs in and you have already checked by means of password_verify that the password entered is actually correct. At that point, if password_needs_rehash returns true, you can put the plain text password through the password_hash function.
ydroneaud at opteya dot com
2 years ago
According to the documentation, it's checking if the given hashed password string is compatible with the provided algorithm (and options, but not salt), eg. it's checking if the hashed password string was generated with the provided algorithm (and options, but not salt).

There's nothing to 'rehash' in its parameters ... especially not the already hashed password string, and the password "stored" in the hashed password string is not supposed to be known, it's not in clear, it's a secret.

The name of the function seems misleading, this function should have been called "password_hash_compatible()" instead.

This function could be use to check if a password database/a hashed password string (hashed by function "password_hash()") need to be upgraded to a stronger password hashing/storage scheme: if the function returns false,  a new password will have to be set for the user, hashed with the new, stronger, algorithm/options.

One should carefully think before using this function to support multiple algorithms/options in one database, eg. support "legacy scheme" passwords + "new scheme" ...
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