PHP password_verify

Summary: in this tutorial, you’ll learn to use the PHP password_verify() function to check if a password matches a hashed password.

Introduction to the PHP password_verify() function

When dealing with passwords, you should never store them in the database as plain text. And you should always hash the passwords using a secure one-way hash algorithm.

PHP provided the built-in password_hash() function that creates a hash from a plain text password. Note that the password_hash() function is a one-way hash function. It means that you cannot find its original value.

To verify if a plain text password matches a hashed password, you must hash the plain text password and compare the hashes.

However, you don’t have to do it manually since PHP provides you with the built-in password_verify() function that allows you to compare a password with a hash:

password_verify(string $password, string $hash): boolCode language: PHP (php)

The password_verify() has two parameters:

• $password is a plain text password to match.
• $hash is a hash created by the password_hash() function.

The password_verify() function returns true if the password matches the hash or false otherwise.

PHP password_verify() function example

The following example uses the password_verify() function to check if the password Password1 matches a hash:

<?php

$hash = '$2y$10$hnQY9vdyZUcwzg2CO7ykf.a4iI5ij4Pi5ZwySwplFJM7AKUNUVssO';
$valid = password_verify('Password1', $hash);

echo $valid ? 'Valid' : 'Not valid';Code language: PHP (php)

Output:

ValidCode language: PHP (php)

In practice, you’ll use the password_verify() function as following to verify a login:

• Find a user from the database by a username (or email)
• Use the password_verify() function to match the user’s provided password with a hashed password.
• If the password matches the hash, you log the user in. Otherwise, you’ll issue an error message.

The code will look like the following:

<?php

// ...

$user = find_user_by_username($username);

if ($user && password_verify($password, $user['password'])) {
    // log the user in
    session_regenerate_id();
    $_SESSION['user_id'] = $user['id'];
} else {
    echo 'Invalid username or password';
}Code language: PHP (php)

In the following tutorial, you’ll learn to use the password_verify() function in the login form.

Summary

• Use the PHP password_verify() function to check if a password matches a hashed password created by the password_hash() function.