Get the md5 of your whole PHP application

md5.php

<?php

function glob_recursive($pattern, $flags = 0) {
    $files = glob($pattern, $flags);
    foreach (glob(dirname($pattern).'/*', GLOB_ONLYDIR|GLOB_NOSORT) as $dir)  {
        $files = array_merge($files, glob_recursive($dir.'/'.basename($pattern), $flags));
    }
    return $files;
}

foreach (glob_recursive('*.php') as $file) {
    $md5[$file] = md5_file($file);
}
echo md5(implode($md5));