自己写的一个mysqli的小函数，增删改查.

//使用方法：$sql = '';  $data = db_switch('you db','select * from tb','2');
function db_switch($db,$sql,$type='2',$utf='utf8'){
        if (empty($sql))
            die('sql is empty');
        switch ($db) {
            case 'your database name':
                return db_connect(ip,user,passwd,db,$sql,$type,$utf);
                break;

            default:
                echo 'please enter you db_name,like bm、shop、live。';
        }
    }

function db_connect($ip,$root,$pass,$db,$sql,$type,$utf){
        $db = @mysqli_connect($ip,$root,$pass,$db) or die("Error " . mysqli_error($link));
        $db->set_charset($utf);
        $data = $db->query($sql);
        $res = array();
        if ($type=='1'){//查询一条数据
            $res = $data->fetch_assoc();
        }elseif($type=='2'){//查询多条
            $res = $data->fetch_all(MYSQLI_ASSOC);
        }elseif ($type=='3'){//更新和删除
            $res = $db->affected_rows;
        }
        $db->close();
        return $res;
    }