Code Issue

My Js Is:

jQuery(document).ready(function($) {
$('#placeorder').click(function(){   alert('6');

    	$.ajax({url:MyAjax.ajaxurl,
action: 'my_action'});
									});

});

and

PHP file is:

// embed the javascript file that makes the AJAX request
wp_enqueue_script( 'my-ajax-request',get_template_directory_uri() . '/js/countclicks.js', array( 'jquery' ) );
// declare the URL to the file that handles the AJAX request (wp-admin/admin-ajax.php)
wp_localize_script( 'my-ajax-request', 'MyAjax', array( 'ajaxurl' => admin_url( 'admin-ajax.php' ) ) );

add_action('wp_ajax_my_action', 'my_action_callback');
add_action('wp_ajax_nopriv_my_action', 'my_action_callback');

function my_action_callback() {

echo "<script Langauage=\"Javasacript\">";
echo ("alert(\"Invalid user, please try again\.\");");
echo "</script>";die();

}

and function file include above PHP file as:
include_once(‘order_submit_inc.php’);

But I can’t execute my PHP function on button click.