Forminator - Limit form submissions per IP for 24 hours.

frmt-limit-form-sub.php

<?php

/**
 * Plugin Name: Forminator
 * Description: Limit form submissions per IP for 24 hours.
 * Author: Konstantinos Xenos @ WPMUDEV
 * Author URI: https://premium.wpmudev.org
 * License: GPLv2 or later
 */

add_filter(
	'forminator_custom_form_submit_errors',
	function( $submit_errors, $form_id, $field_data_array ) {
		// Add your form IDs here.
		$form_ids = array( 49, 15, 20 );

		// Change this to the message that you want to show.
		$message = 'You cannot submit more than 1 time within 24 hours.';

		if ( in_array( intval( $form_id ), $form_ids, true ) ) {

			$user_ip = Forminator_Geo::get_user_ip();

			if ( ! empty( $user_ip ) ) {
				$last_entry = Forminator_Form_Entry_Model::get_last_entry_by_ip_and_form( $form_id, $user_ip );

				if ( ! empty( $last_entry ) ) {
					$entry        = Forminator_API::get_entry( $form_id, $last_entry );
					$current_time = strtotime( date( 'Y-m-d H:i:s' ) );
					$future_time  = strtotime( '+1 day', strtotime( $entry->date_created_sql ) );

					if ( $current_time < $future_time ) {
						$submit_errors[]['submit'] = $message;
					}
				}
			}

		}

		return $submit_errors;
	},
	15,
	3
);