WP Ajax

ajax.js

jQuery(document).ready(function($) {
  
  var data = {
		action: 'smart_ajax', // the action as defined on line 8 of the PHP file
		myVar: 'Hello World' // will be sent to the php within the $_POST global
	};

	$.post(SmartAjax.ajax, data, function(response) {

		console.log(response);

	});
});

ajax.php

function smn_ajax() {
  
  echo $_POST['myVar'];

	die(); // die at end to return proper results
}

add_action( 'wp_ajax_smart_ajax', 'smart_ajax' ); // for logged in users
add_action( 'wp_ajax_nopriv_smart_ajax', 'smart_ajax' ); // for non-logged in users

// enqueue script and localize it to get the admin ajax
function smart_scripts() {
	wp_enqueue_script('ajax-script', get_template_directory_uri() . '/js/ajax.js', array('jquery'), false, true);
	wp_localize_script( 'custom-script', 'SmartAjax', array('ajax' => admin_url('admin-ajax.php')) );
}
add_action( 'wp_enqueue_scripts', 'smart_scripts' );