Noddity PHP thing

<?php
/*
Based on some other things I've seen online.
1: Edit the vars
2: Put on server somewhere accessible, e.g. your site folder as github.php
3: chmod +x github.php
4: Repo settings, add webhook to that url
*/

$LOCAL_ROOT         = "/home/username/site.com";
$LOCAL_REPO_NAME    = "content";
$LOCAL_REPO         = "{$LOCAL_ROOT}/{$LOCAL_REPO_NAME}";
$REMOTE_REPO        = "https://github.com/username/repo.git";
$BRANCH             = "master";

if ( $_POST['payload'] ) {
  if( file_exists($LOCAL_REPO) ) {
    shell_exec("cd {$LOCAL_REPO} && git pull");
    die("done " . mktime());
  } else {
    shell_exec("cd {$LOCAL_ROOT} && git clone {$REMOTE_REPO} {$LOCAL_REPO_NAME}");
    die("done " . mktime());
  }
}