WordPress Ajax Form Submit Example

form.php

<div class="my-form-wrap">
   
    <form class="custom-form-class" action="#" autocomplete="off" method="POST">

    	<!-- Action is here but hidden. This will be use in php side -->
    	<input type="hidden" name="action" value="sample_custom_form_action">

        <input class="input" type="text" spellcheck="false" name="name" placeholder="Name" required>
        <input class="input" type="email" spellcheck="false" name="email" placeholder="E-mail" required>

        <label class="ans">Yes
            <input type="radio" name="radio">
            <span class="checkmark"></span>
        </label>

        <label class="ans">No
            <input type="radio" name="radio">
            <span class="checkmark"></span>
        </label>
        <button> SUBMIT </button>
   </form>
</div>


<script>

	// Javascript to send ajax request
	jQuery(document).on('submit', '.custom-form-class', function(e){
		let formData = jQuery(this).serialize();

		// Change ajax url value to your domain
		let ajaxurl = 'http://YOURSITE.COM/wp-admin/admin-ajax.php';

		// Send ajax
		jQuery.post(ajaxurl, data, function(response) {
			alert('Got this from the server: ' + response);
		});
	});
</script>

function.php

<?php
add_action( 'wp_ajax_sample_custom_form_action', 'prefix_save_custom_form_data' );
add_action( 'wp_ajax_nopriv_sample_custom_form_action', 'prefix_save_custom_form_data' );
function prefix_save_custom_form_data(){
	global $wpdb;
	
	// Get the values
	$name  = isset( $_POST['name'] ) ? sanitize_text_field( $_POST['name'] ) : ''; // Empty value if data not set
	$email = isset( $_POST['email'] ) ? sanitize_email( $_POST['email'] ) : ''; // Empty value if data not set
	$radio = isset( $_POST['radio'] ) ? sanitize_text_field( $_POST['radio'] ) : ''; // Empty value if data not set

	// Assume your table name is wp_customform
	$your_table_name = $wpdb->prefix . 'customform';

	// Insert into database
	$wpdb->insert(
		$your_table_name, 
		array(
			'name' => $name,
			'email' => $email,
			'radio' => $radio,
		)
	);

	// Send insert id as ajax response
	echo $wpdb->insert_id;

	// Use die to stop the ajax action
	wp_die();
}