PHP获取今天开始和结束的时间戳

$t = time();
$start = mktime(0,0,0,date("m",$t),date("d",$t),date("Y",$t));
$end = mktime(23,59,59,date("m",$t),date("d",$t),date("Y",$t));

echo "一周后:".date("Y-m-d",strtotime("+1 week")). "
";     
echo "一周零两天四小时两秒后:".date("Y-m-d G:H:s",strtotime("+1 week 2 days 4 hours 2 seconds")). "
";     
echo "下个星期四:".date("Y-m-d",strtotime("next Thursday")). "
";     
echo "上个周一:".date("Y-m-d",strtotime("last Monday"))."
";     
echo "一个月前:".date("Y-m-d",strtotime("last month"))."
";     
echo "一个月后:".date("Y-m-d",strtotime("+1 month"))."
";     
echo "十年后:".date("Y-m-d",strtotime("+10 year"))."
";