wp_password_needs_rehash()

wp_password_needs_rehash() — Checks whether a password hash needs to be rehashed. Passwords are hashed with bcrypt using the default cost. A password hashed in a prior version of WordPress may still be hashed with phpass and will need to be rehashed. If the default cost or algorithm is changed in PHP or WordPress then a password hashed in a previous version will need to be rehashed. Note that, just like wp_check_password(), this function may be used to check a value that is not a user password.

Inputs: $hash (string): Hash of a password to check. $user_id (string|int): Optional. ID of a user associated with the password.

Returns bool: Whether the hash needs to be rehashed.