生成月初月末便于拼接sql

 for ($i=1; $i < 13; $i++) { 

     $date = strtotime(date("2015-$i-01"));

     $firstday = date("Y-m-01",$date);

     $lastday = date("Y-m-t",$date);

     echo $firstday.'==='.$lastday.'<br/>';
 }