PHP: Deleting all files from a folder that reached a certain age (x hours/days/weeks/months/years)

/**
     * @param $folder the folder in which the old files are supposed to get purged
     * @param $maximumAge maximum file age in seconds
     * @param $ignoreList array() of filenames that should get ignored
     */
    public function deleteOldFiles($folder, $maximumAge,$ignoreList){
        $dir=scandir($folder);
        foreach($dir as $file){
            $secretFileTime=$this->getCorrectMTime($folder.$file);
            $fileAge=time()-$secretFileTime;
            if(($file!='..')&&($file!='.')&&($file!='index.html')&&(!in_array($file,$ignoreList))){
                if($fileAge>$maximumAge){
                    unlink($folder.'/'.$file);
                    //echo "
deleting ".$folder.$file." because it has the age: ".$fileAge;
                }else{
                    //echo "
keeping ".$folder.$file." because it has the age: ".$fileAge;
                }
            }else{
                //echo "
ignored ".$file;
            }
        }
    }
 
public function getCorrectMTime($filePath){
 
        $time = filemtime($filePath);
 
        $isDST = (date('I', $time) == 1);
        $systemDST = (date('I') == 1);
 
        $adjustment = 0;
 
        if($isDST == false && $systemDST == true)
            $adjustment = 3600;
 
        else if($isDST == true && $systemDST == false)
            $adjustment = -3600;
 
        else
            $adjustment = 0;
 
        return ($time + $adjustment);
    }