Which hook should be used to validate custom form fields on the login form?

Question

I've added a custom input field with login_form hook.

So, I need to process the post data to validate. I've used the lostpassword_post for lostpassword_form and works great, but I cant find a hook to validate my data at login form.

Any Ideas?

Answer 1

Use the action 'login_init' to catch all calls to wp-login.php.

Sample code:

add_action( 'login_init', 'wpse_51227_validate_custom_field' );

function wpse_51227_validate_custom_field()
{
    if ( ! isset ( $_POST['special_custom'] )
        return;

    if ( ! is_numeric( $_POST['special_custom'] )
        // handle the error
}

There are two important global variables available:

• $errors is an instance of WP_Error. Maybe you want to use it to store error data.
• $action is the current action. Maybe you want to rest it to login to prevent a redirect if the user input is invalid.

Answer 2

Haven't really tested this but I'm just guessing by how I do it with the registration & profile pages.

Try something like this:

function my_login_errors( $errors ) {
    if ( empty( $_POST['custom_field'] ) )
        $errors->add( 'empty_custom_field', '<strong>ERROR</strong>: Please enter some info.' );
    return $errors;
}
add_filter( 'login_errors', 'my_login_errors' );

Note: Modify the custom_field part and the message accordingly.