$sqlCount = "SELECT count(id) FROM 表名 WHERE typeid= 1"; //typeid是栏目id

 //在数据库使用查询语句查询，然后拿到结果
 $resultCount = $demo-> query($sqlCount);
 
 //输出中长度
 if($resultCount){
	 $total = $resultCount -> fetch_assoc();
	 //count(id)总数
	 $dataCount = $total[count(id)];
 }
 
 //把赋值给返回数据的total
 $outData['total'] = (int)$total["count(id)"];