class nmdb

{

private $link;

static private $_instance;

// 连接数据库

private function __construct($host, $username, $password)

{

$this->link = mysql_connect($host, $username, $password);

$this->query("SET NAMES 'utf8'", $this->link);

//echo mysql_errno($this->link) . ": " . mysql_error($link). "n";

//var_dump($this->link);

return $this->link;

}

private function __clone(){}

public static function get_class_nmdb($host, $username, $password)

{

//$connector = new nmdb($host, $username, $password);

//return $connector;

if( FALSE == (self::$_instance instanceof self) )

{

self::$_instance = new self($host, $username, $password);

}

return self::$_instance;

}

// 连接数据表

public function select_db($database)

{

$this->result = mysql_select_db($database);

return $this->result;

}

// 执行SQL语句

public function query($query)

{

return $this->result = mysql_query($query, $this->link);

}

// 将结果集保存为数组

public function fetch_array($fetch_array)

{

return $this->result = mysql_fetch_array($fetch_array, MYSQL_ASSOC);

}

// 获得记录数目

public function num_rows($query)

{

return $this->result = mysql_num_rows($query);

}

// 关闭数据库连接

public function close()

{

return $this->result = mysql_close($this->link);

}

}

?>

这个类的使用如下：

$connector = nmdb::get_class_nmdb($host, $username, $password);

$connector -> select_db($database);

下面的类也可以参考下：

/*

* mysql 单例

*/

class mysql{

private $host ='localhost'; //数据库主机

private $user = 'root'; //数据库用户名

private $pwd = ''; //数据库用户名密码

private $database = 'imoro_imoro'; //数据库名

private $charset = 'utf8'; //数据库编码，GBK,UTF8,gb2312

private $link; //数据库连接标识;

private $rows; //查询获取的多行数组

static $_instance; //存储对象

/**

* 构造函数

* 私有

*/

private function __construct($pconnect = false) {

if (!$pconnect) {

$this->link = @ mysql_connect($this->host, $this->user, $this->pwd) or $this->err();

} else {

$this->link = @ mysql_pconnect($this->host, $this->user, $this->pwd) or $this->err();

}

mysql_select_db($this->database) or $this->err();

$this->query("SET NAMES '{$this->charset}'", $this->link);

return $this->link;

}

/**

* 防止被克隆

*

*/

private function __clone(){}

public static function getInstance($pconnect = false){

if(FALSE == (self::$_instance instanceof self)){

self::$_instance = new self($pconnect);

}

return self::$_instance;

}

/**

* 查询

*/

public function query($sql, $link = '') {

$this->result = mysql_query($sql, $this->link) or $this->err($sql);

return $this->result;

}

/**

* 单行记录

*/

public function getRow($sql, $type = MYSQL_ASSOC) {

$result = $this->query($sql);

return @ mysql_fetch_array($result, $type);

}

/**

* 多行记录

*/

public function getRows($sql, $type = MYSQL_ASSOC) {

$result = $this->query($sql);

while ($row = @ mysql_fetch_array($result, $type)) {

$this->rows[] = $row;

}

return $this->rows;

}

/**

* 错误信息输出

*/

protected function err($sql = null) {

//这里输出错误信息

echo 'error';

exit();

}

}

//用例

$db = mysql::getInstance();

$db2 = mysql::getInstance();

$data = $db->getRows('select * from blog');

//print_r($data);

//判断两个对象是否相等

if($db === $db2){

echo 'true';

}

?>