GitHub Webhook Handler

github-webhook-handler.php

<?php

/**
 * GitHub webhook handler template.
 * 
 * @see     https://docs.github.com/webhooks/
 * @author  Miloslav Hůla (https://github.com/milo)
 */

$hookSecret = 's.e.c.r.e.t';  # set NULL to disable check


set_error_handler(function($severity, $message, $file, $line) {
	throw new \ErrorException($message, 0, $severity, $file, $line);
});

set_exception_handler(function($e) {
	header('HTTP/1.1 500 Internal Server Error');
	echo "Error on line {$e->getLine()}: " . htmlSpecialChars($e->getMessage());
	die();
});

$rawPost = null;
if ($hookSecret !== null) {
	if (!isset($_SERVER['HTTP_X_HUB_SIGNATURE'])) {
		throw new \Exception("HTTP header 'X-Hub-Signature' is missing.");
	} elseif (!extension_loaded('hash')) {
		throw new \Exception("Missing 'hash' extension to check the secret code validity.");
	}

	list($algo, $hash) = explode('=', $_SERVER['HTTP_X_HUB_SIGNATURE'], 2) + array('', '');
	if (!in_array($algo, hash_algos(), true)) {
		throw new \Exception("Hash algorithm '$algo' is not supported.");
	}

	$rawPost = file_get_contents('php://input');
	if (!hash_equals($hash, hash_hmac($algo, $rawPost, $hookSecret))) {
		throw new \Exception('Hook secret does not match.');
	}
};

if (!isset($_SERVER['CONTENT_TYPE'])) {
	throw new \Exception("Missing HTTP 'Content-Type' header.");
} elseif (!isset($_SERVER['HTTP_X_GITHUB_EVENT'])) {
	throw new \Exception("Missing HTTP 'X-Github-Event' header.");
}

switch ($_SERVER['CONTENT_TYPE']) {
	case 'application/json':
		$json = $rawPost ?: file_get_contents('php://input');
		break;

	case 'application/x-www-form-urlencoded':
		$json = $_POST['payload'];
		break;

	default:
		throw new \Exception("Unsupported content type: $_SERVER[CONTENT_TYPE]");
}

# Payload structure depends on triggered event
# https://developer.github.com/v3/activity/events/types/
$payload = json_decode($json);

switch (strtolower($_SERVER['HTTP_X_GITHUB_EVENT'])) {
	case 'ping':
		echo 'pong';
		break;

//	case 'push':
//		break;

//	case 'create':
//		break;

	default:
		header('HTTP/1.0 404 Not Found');
		echo "Event:$_SERVER[HTTP_X_GITHUB_EVENT] Payload:\n";
		print_r($payload); # For debug only. Can be found in GitHub hook log.
		die();
}

Thanks for feedback!
I cannot recall, why I used HTTP_CONTENT_TYPE. So I updated gist to use CONTENT_TYPE and hash_equals(). Thank you.