Login by email only by Amiru アミル さん

/**

 * Allow login with email only.. By Amiru アミル さん

 */

// 1. Authenticate user by email if username is not provided.

add_filter('authenticate', 'authenticate_with_email', 20, 3);

function authenticate_with_email($user, $username, $password) {

    if (empty($username) && !empty($password)) {  // Check if username is empty but password is provided.

        // Retrieve user by email.

        $user_by_email = get_user_by('email', $password); // Use password field for email lookup temporarily.

        if ($user_by_email && wp_check_password($password, $user_by_email->user_pass, $user_by_email->ID)) {

            return $user_by_email; // User authenticated successfully.

        } else {

            // Set a custom error message.  Important for user experience!

            $user = new WP_Error('invalid_email_or_password', __('<strong>ERROR</strong>: Invalid email or password.'));

            return $user;

        }

    }

    return $user; // Return original $user if username was provided or authentication failed in other ways.

}

// 2. Modify the username field label on the login form.

add_filter( 'gettext', 'change_username_label', 20, 3 );

function change_username_label( $translated_text, $text, $domain ) {

    if ( 'Username or Email' === $text && 'default' === $domain && is_page('wp-login.php')) { //Target the login page

        $translated_text = 'Email Address';

    } elseif ('Username' === $text && 'default' === $domain && is_page('wp-login.php')) { // Fallback if the above doesn't work.

      $translated_text = 'Email Address';

    }

    return $translated_text;

}

//3. Optional:  Pre-fill the email field if it's passed as a query parameter. Useful for password reset links.

add_action('login_form', 'prefill_email_field');

function prefill_email_field() {

  if (isset($_GET['email'])) {

    $email = sanitize_email($_GET['email']);

    ?>

    <script type="text/javascript">

      document.getElementById('user_login').value = '<?php echo esc_js($email); ?>';

    </script>

    <?php

  }

}

// 4.  Prevent login by username (optional but recommended for security).

add_filter('authenticate', 'prevent_username_login', 30, 3); //High priority to run after email auth

function prevent_username_login($user, $username, $password) {

    if (!empty($username) && !is_email($username)) { //If it's not empty and not an email

      $user = new WP_Error('invalid_username', __('<strong>ERROR</strong>: You can only log in with your email address.'));

      return $user;

    }

    return $user;

}

// 5. Change "Lost your password?" link to use the email field, if the email is present in the login form.

add_filter( 'lostpassword_url', 'custom_lostpassword_url', 10, 2 );

function custom_lostpassword_url( $lostpassword_url, $redirect ) {

    if (isset($_POST['user_login']) && is_email($_POST['user_login'])) {

        $email = $_POST['user_login'];

        $lostpassword_url = add_query_arg( 'user_login', $email, $lostpassword_url ); //Adds email to the URL

    }

    return $lostpassword_url;

}