Sometimes clients are unable to login to their WordPress site for whatever reason (can’t perform forgot password, lost email or malware infected). As long as I have access to the files I can get around this by placing a simple code in WordPress to log me in with just the admin username.

I usually place this code anywhere in functions.php on the active theme. After the code is inserted, fill in $user variable and then login by navigating to https://www.your-site.com/?action=forceLogin. If logged in correctly you should see the user details from the database.

<?php

$user = '';

if (@$_REQUEST['action'] == 'forceLogin') {
    $loginuser = get_userdatabylogin( $user );
    $user_id = $loginuser->ID;
    wp_set_current_user( $user_id, $loginuser );
    wp_set_auth_cookie( $user_id );

    print_r($loginuser);
    die('logged in');
}

So far tested on WordPress 4.9.8-5.0.3