php取當天的0點和23點59分59秒的時間戳方法

$year = date("Y");
$month = date("m");
$day = date("d");
$start = mktime(0,0,0,$month,$day,$year);//當天開始時間戳
$end= mktime(23,59,59,$month,$day,$year);//當天結束時間戳