Gravity Forms - Populate the Name Field from a GET variable which is the user ID

functions.php

add_filter( 'gform_pre_render_6', 'populate_user_info' );
add_filter( 'gform_pre_validation_6', 'populate_user_info' );
add_filter( 'gform_pre_submission_filter_6', 'populate_user_info' );
add_filter( 'gform_admin_pre_render_6', 'populate_user_info' );

function populate_user_info( $form ) {
	$userid = sanitize_text_field($_GET['userid']);
  foreach ( $form['fields'] as &$field ) {
		if ($field->type == 'name'){
			$field->inputs[1]['defaultValue'] = get_first_name($userid);
			$field->inputs[3]['defaultValue'] = get_last_name($userid);
		}
	}
	return $form;
}

function get_first_name($userid){
	$userinfo = get_userdata($userid);
	return $userinfo->first_name;
}
function get_last_name($userid){
	$userinfo = get_userdata($userid);
	return $userinfo->last_name;
}