Date Diff PHP

function dateDiff($interval,$dateTimeBegin,$dateTimeEnd){
        $dateTimeBegin=strtotime($dateTimeBegin);
        if($dateTimeBegin === -1) { return("..begin date Invalid"); }
        $dateTimeEnd=strtotime($dateTimeEnd);
        if($dateTimeEnd === -1) { return("..end date Invalid"); }
        $dif=$dateTimeEnd - $dateTimeBegin;
        switch($interval){
            case "s"://seconds
            return($dif);
            break;
            case "n"://minutes
            return(floor($dif/60)); //60s=1m
            break;
            case "h"://hours
            return(floor($dif/3600)); //3600s=1h
            break;
            case "d"://days
            return(floor($dif/86400)); //86400s=1d
            break;
            case "ww"://Week
            return(floor($dif/604800)); //604800s=1week=1semana
            break;
            case "m": //similar result "m" dateDiff Microsoft
            $monthBegin=(date("Y",$dateTimeBegin)*12)+date("n",$dateTimeBegin);
            $monthEnd=(date("Y",$dateTimeEnd)*12)+date("n",$dateTimeEnd);
            $monthDiff=$monthEnd-$monthBegin;
            return($monthDiff);
            break;
            case "yyyy": //similar result "yyyy" dateDiff Microsoft
            return(date("Y",$dateTimeEnd) - date("Y",$dateTimeBegin));
            default:
            return(floor($dif/86400)); //86400s=1d
        }
    }