Starting point for a PHP API Endpoint.

php-endpoint.php

<?php
header("Content-Type: application/json; charset=UTF-8");

ini_set('display_errors', 0);
ini_set('log_errors', 1);
error_reporting(E_ALL);

/* Vars
   -------------------------------------- */

$request = $_GET['request'];
$return = array('code' => 200, 'message' => '');

/* Check API Key 
   -------------------------------------- */

$api_key = 'your-test-api-key';
$headers = apache_request_headers();

if ( isset($headers['wsm-authorization']) ) {
  if ( $api_key != 'your-valid-api-key' ) {
    // The key is invalid, return an error response
    http_response_code(401);
    echo json_encode(array("message" => "Invalid API Key."));
    exit();
	}
}

/* Endpoints 
   -------------------------------------- */

switch ($request) {
  case 'test':
    $return = array('code' => 200, 'message' => 'test');
  break;

  default: 
    $return = array('code' => 200, 'message' => 'hello.');
  break;
}

exit(json_encode($return));