PHP 连接MySQL 的单态类

<?php
/**
 * author: xueming
 */
class MySQLConnFactory
{
	private $conn;
	static private $_mysqlconn;

	//Construct-->connect DB
	private function __construct($host,$username,$password)
	{
		$this->conn = mysql_connect($host,$username,$password);
		$this->query("SET NAMES 'utf8'");
		return $this->conn;
	}
	
    private function __clone(){}

	public static function getSingleMySQLConn($host,$username,$password)
	{
		if(FALSE==(self::$_mysqlconn instanceof self))
		{
			self::$_mysqlconn = new self($host,$username,$password);
		}
		return self::$_mysqlconn;
	}

	//select DB
	public function select_db($database)
	{
		$this->result = mysql_select_db($database);
		return $this->result;
	}
	
	//Query 
	public function query($query)
	{
		return $this->result = mysql_query($query, $this->conn);
	}
	
	//fetch result
	public function fetch_array($fetch_array)
	{
		return $this->result = mysql_fetch_array($fetch_array, MYSQL_ASSOC);
	}
	
	//close
	public function close()
	{
		return $this->result = mysql_close($this->conn);
	}
}
?>

调用方式如下

    $sql = "select * from test";
    $connector = MySQLConnFactory::getSingleMySQLConn($db_server,$db_user,$db_pwd);
    $connector -> select_db($db_name);
    $result = $connector -> query($sql);