WordPress admin-ajax.php is dying “0” without processing function

I am trying to learn how to process AJAX requests in WordPress the correct way. To do this I am adapting this tutorial to create a super simple AJAX request to place the ID of a post (from a link) into my page content.

The Logic

1. When the #our-work a links are clicked [js]
2. Get the post ID (from the data-id attribute) & store it as postID variable [js]
3. Pass postID via an AJAX (using the WP’s admin-ajax.php file) [js]
4. The example_ajax_request function will pick up the ID & simply echo it [php]
5. If successful, append the server response to the #hero div.

I realise this has no benefit but once I have that working I will amend the function to serve a real purpose.

My Code

Here is a copy of the function I have created in the plugins folder:

wp_enqueue_script( 'my-ajax-request', plugin_dir_url( __FILE__ ) . 'acl-plugin.js', array( 'jquery' ) );

wp_localize_script( 'my-ajax-request', 'MyAjax', array( 'ajaxurl' => admin_url( 'admin-ajax.php' ) ) );

function example_ajax_request() {
    if ( isset($_REQUEST) ) {
        $postID = $_REQUEST['postID'];
        echo $postID;
    }
    die();
}
add_action( 'wp_ajax_nopriv_example_ajax_request', 'example_ajax_request' );

And here is a copy of the JS file

jQuery(document).ready(function($) {
    $('#our-work a').click( function() {
        var postID = $(this).attr("data-id");

        $.ajax({
            url: MyAjax.ajaxurl,
            data: {
                'action':'example_ajax_request',
                'postID' : postID
            },
            success:function(data) {
                $('#hero').append( "Well this seems to work" + data );
            },
            error: function(errorThrown){
                console.log("This has thrown an error:" + errorThrown);
            }
        });
        return false;
    });
});

The Problem

Upon clicking the link the JS does fire but yields the following response:

<div id="hero">
    Well this seems to work 0
</div>

Using an alert I know the ID is being picked up before the AJAX request. So the problem is in my function. To find out more, I (temporarily) tweaked WP’s admin-ajax.php file, so that I could find out which die(); was yielding the response of “0”.

It is the very last one in the file which I thought wouldn’t fire as I have a die(); command in my own function. Can someone please point out where I am going wrong?