function getWeekCount($date,&$w=false)
{
    $t=strtotime(date("Y-m-01",strtotime($date)));
    $j=1;//주차
    $total_week=array();
    for($day=0;$day<=31;$day++){
        $t2=strtotime("+{$day}day",$t);
        $w=date("w",$t2);
        if($w==0 && $day!=0) $j++;
        if (date("Y-m-d",$t2)>=substr($date,0,10)) break;
    }
$w=date("w",strtotime($date));
return $j;
}

echo "주차 : ",getWeekCount('2018-03-11',$w),"<BR>";
echo "요일 : $w <BR>";

작성 : 하우코드