HOWTO: Create a WordPress AJAX Endpoint for a JSON Payload

wordpress-ajax-endpoint.php

<?php

/*
* In this GIST, we register a webhook that will be available for other applications to call e.g. JSON
* This code could be added to functions.php or your own plugin.
*/

//Register an end point for logged in users
add_action("wp_ajax_my_webhook", "my_webhook");
//Register an end point for logged out users
add_action("wp_ajax_nopriv_my_webhook", "my_webhook");

/* This AJAX end point will be available at:
* https://www.domain.com/wp-admin/admin-ajax.php?action=my_webhook
*/

/* My function assumes we'll be recieving a JSON Payload */
function my_webhook () {

    //Decode the incoming JSON Payload
	  $data = json_decode(file_get_contents('php://input'), true);
    
    //Output to the log (For Debug, not mandatory)
    error_log(print_r($data,true));
    
    //Set up for scheduled event
    $data = array($data);
    
    //Set up a schedule event in 15 seconds to process the data. NEVER process synchronously!
    wp_schedule_single_event( time()+15, 'do_json_processing', $data );
	
    //Set a 200 (Success Header)
	  status_header(200);

    /* Always die for AJAX */
	  die();
}

?>