Simple PHP Webhook for Dialogflow v1

dialogflow_webhook_v1.php

function processMessage($update) {
   	if($update["result"]["action"] == "test.welcome"){
		sendMessage(array(
		"source" => $update["result"]["source"],
		"speech" => "Hello World!",
		"displayText" => "Hello World!",
		"contextOut" => array()
));
}
}
function sendMessage($parameters) {
	echo json_encode($parameters);
}
$update_response = file_get_contents("php://input");
$update = json_decode($update_response, true);
if (isset($update["result"]["action"])) {
	processMessage($update);
}