How to make last name field required (where to put the PHP snippet?)

Hi there,

We are required to have last names when collecting donations for our financial disclosure.

I saw a previous thread that provided a PHP snippet for making last name fields required on our form.

Based on the description, it sounds like this snippet will do what I need it to do but I don’t have much experience with PHP. I don’t know which .php file to update in the plugin or where in that file I would need to insert the code (I’m not sure if PHP syntax requires things in a certain order).

Any clarification would be greatly appreciated. We need to have this form fully live and functional asap.

For reference this was the code:

<?php

/**
 * Require Last Name Snippet.
 *
 * Adds asterisk and error validation to the last name field of all Give forms.
 *
 * @param $required_fields
 * @param $form_id
 *
 * @return mixed
 */
function give_require_last_name( $required_fields, $form_id ) {

	$required_fields['give_last'] = array(
		'error_id'      => 'invalid_last_name',
		'error_message' => __( 'Please enter your last name', 'give' )
	);
	
	//If restricting by gateway:
	$stripe = give_is_gateway_active( 'give-stripe' );

	if ($stripe) {
		$required_fields['card_state'] = array(
			'error_id'      => 'invalid_card_state',
			'error_message' => __( 'Please enter your Credit Cards billing State.', 'give-stripe' )
		);
	}

	return $required_fields;
}

add_filter( 'give_donation_form_required_fields', 'give_require_last_name', 10, 2 );

The page I need help with: [log in to see the link]