<?php 
----mysql baglantisi---

$bugun= date("Y-m-d");
$yenitarih = strtotime('-90 day',strtotime($bugun));
$yenitarih = date('Y-m-d' ,$yenitarih );

$sql = "select fatura,id,count(*)  as toplam from faturalar WHERE date_format( tarih, '%Y-%c-%d' ) between '$yenitarih' and '$bugun' group by fatura ORDER BY toplam DESC limit 1 "; 
if($query = mysql_query($sql)) 
{ 
 while ($row = mysql_fetch_assoc($query)) 
{ 
----- verileri cek------
}     
}  
?>