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/>';
}