$sumbybillid = mysql_query("Select sum(PRICE) from myorder where BILLID = 'MD0005' group by BILLD ") or die ('Error query: ' . mysql_error());;
echo $sumbybillid ;
คือถ้านำ Select sum(PRICE) from myorder where BILLID = 'MD0005' group by BILLD ไป รันใน mysql จะได้ค่าที่ถูกต้องไม่มีปัญหา
$rs = mysql_query("Select sum(PRICE) from myorder where BILLID = 'MD0005' group by BILLD ") or die ('Error query: ' . mysql_error());;
$data=mysql_fetch_array($rs);
echo $data[0] ;