GitHub Web Hook for updating a repo

pull.php

<?php
header('Content-Type: text/plain');
$secret = 'xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx';
$branch = 'master';

$hub_signature = @$_SERVER['HTTP_X_HUB_SIGNATURE'];
if (!$hub_signature) {
	http_response_code(403);
	exit('missing signature');
}
list($algo, $hash) = explode('=', $hub_signature, 2);

try {
	$payload = file_get_contents('php://input');
	$data = json_decode($payload);
} catch (Exception $e) {
	http_response_code(400);
	exit('invalid payload');
}

if ($hash !== hash_hmac($algo, $payload, $secret)) {
	http_response_code(403);
	exit('invalid secret');
}

switch (@$_SERVER['HTTP_X_GITHUB_EVENT']) {
case 'ping':
	echo $data->zen;
	break;

case 'push':
	if ($data->ref !== "refs/heads/$branch") {
		exit("branch not $branch, nothing done");
	}

	$clone_url = escapeshellarg($data->repository->clone_url);
	$sha = escapeshellarg($data->after);
	passthru("git fetch $clone_url $branch; git reset --hard $sha", $ret);
	if ($ret != 0) {
		http_response_code(500);
	}
	break;

default:
	http_response_code(204);
}