php 判断时间是否超过

   $str="2014-10-11";
   echo "".strtotime($str);
   echo "<br/>";
   echo "".time('Y-m-d');
    echo "<br/>";
   if(strtotime($str)>time('Y-m-d')){
        echo "未过期";
   }else{
   	   echo "过期";
   }