PHP封装了一个DB数据库mysql的类

conn = mysql_connect(DB_HOST, DB_USER, DB_PASS) or die("connect failed" . mysql_error()); 
 
 //选择数据库
 
 mysql_select_db(DB_DATABASENAME, $this->conn); 
 
 //设置编码格式
 
 mysql_query("SET NAMES utf8");
 
 //var_dump($conn);
 
 $this->tablename=$tablename;
 
 }
 
 //设置sql语句
 
 private function setsql($sql)
 
 {
 
 $this->sql=$sql;
 
 }
 
 
 
 //设置条件语句
 
 public function where($where)
 
 {
 
 $this->where=" where ".$where; 
 return $this;
 
 }
 //按指定字段
 
 public function field($keyword)
 
 {
 
 $this->fieldname=$keyword;
 
 return $this;
 
 }
 
 //设置连接查询表
 
 public function table($table1,$table2,$field,$bool)
 
 {
 
 $this->tablename="$table1 LEFT JOIN $table2 ON $table1.$field$bool$table2.$field";
 
 //print_r($this->tablename);
 
 return $this;
 
 }

 //设置多表查询
 
 public function addtable($table1,$table2,$field,$bool)
 
 {
 
 $this->tablename.=" LEFT JOIN $table2 ON $table1.$field$bool$table2.$field";
 
 //print_r($this->tablename);
 
 return $this;
 
 }
 //设置连接查询表
 
 ##SELECT * FROM 【wx_order LEFT JOIN wx_shopcar ON wx_shopcar.oid=wx_order.oid and wx_order.uid=wx_shopcar.uid LEFT JOIN wx_goods ON wx_shopcar.gid=wx_goods.gid】 WHERE wx_order.oid=1 and wx_order.uid=3
 
 public function settable($sql)
 
 {
 
 $this->tablename=$sql;
 
 //print_r($this->tablename);
 
 return $this;
 
 }
 
 
 
 //查询所有数据库 以数组形式