php获取前一天或后一天的日期代码

PHP 判断前/后一天，或前后多少天的代码：

"; 

    echo "今天:",date("Y-m-d",strtotime("18 june 2008")),"
"; 

    echo "昨天:",date("Y-m-d",strtotime("-1 day")), "
"; 

    echo "明天:",date("Y-m-d",strtotime("+1 day")), "
"; 

    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"))."
";

判断一个日期距今天还有多少天：