Example script to use with github webhooks to update a site when pushing on master

gistfile1.php

<?php
/* Webhook to update a repo for each push on GitHub. */

date_default_timezone_set('Europe/Paris');

$header_match = 'HTTP_X_HUB_SIGNATURE';
$secret_key   = 'my_secret_key_in_github_webhook';
$branch       = 'master';

function logHookResult($message , $success = false) {
    $log_headers = "$message\n";
    if (! $success) {
        foreach ($_SERVER as $header => $value) {
           $log_headers .= "$header: $value \n";
        }
    }
    file_put_contents(__DIR__ . '/github_log.txt', $log_headers);
}

if (isset($_SERVER[$header_match])) {
    $validation = hash_hmac(
        'sha1',
        file_get_contents("php://input"),
        $secret_key
    );

    if ($validation == explode('=', $_SERVER[$header_match])[1]) {
        exec("git checkout $branch ; git pull origin $branch");
        logHookResult('Last update: ' . date('d-m-Y H:i:s'), true);
    } else {
        logHookResult('Invalid github secret');
    }
} else {
    logHookResult("{$header_match} header missing, define a secret key for your project in GitHub");
}