private function _getFileLastModifiedTimesIndentifier($_file_paths = array()) { // Creates a unique string identifier representing the modified times of files // passed to it as a parameter. $_file_paths = !is_array($_file_paths) ? array($_file_paths) : $_file_paths; $iden = ''; foreach ($_file_paths as $file) { if (App\Files::exists($file)) { $time = App\Files::lastModified($file); if ($time === false) { xplog('Unable to get the last modified time of file "' . $file . '"', __METHOD__); continue; } $iden .= $time; } else { xplog('Found that file "' . $file . '" does not exist when trying to get its last modified time.', __METHOD__); } } return md5($iden); }