AfterShip webhook for WordPress

functions.php

<?php
//Aftership Automatic Tracker
add_action('wp_head','trackship_catcher');
function trackship_catcher() {
    if(isset($_GET['webhook-listener']) && $_GET['webhook-listener'] == 'trackship') {
    
        //Get and decode JSON
        $str = file_get_contents("php://input");
        $json = json_decode($str, true);
    
        //Extract Required Variables
        $trackingnumber = $json['msg']['tracking_number'];
        $shipmentstatus = $json['msg']['tag'];
        $shiporderid = $json['msg']['order_id'];

        //Update to the latest shipment status
        update_post_meta( $shiporderid, '_shipment_status', $shipmentstatus );

        //Check if shipping status =  InTransit, set order status to complete
        if($shipmentstatus == 'InTransit'):
            $order = wc_get_order( $shiporderid );
            $order->update_status( 'completed' );
        endif;
    
    }
}