singleton单例模式

<?php

class Db {
static private $_instance;
static private $_connectSource;
private $_dbConfig = array(
'host' => '127.0.0.1',
'user' => 'root',
'password' => '',
'database' => 'video',
);

private function __construct() {
}

static public function getInstance() {
if(!(self::$_instance instanceof self)) {
self::$_instance = new self();
}
return self::$_instance;
}

public function connect() {
if(!self::$_connectSource) {
self::$_connectSource = @mysql_connect($this->_dbConfig['host'], $this->_dbConfig['user'], $this->_dbConfig['password']);

if(!self::$_connectSource) {
throw new Exception('mysql connect error ' . mysql_error());
//die('mysql connect error' . mysql_error());
}

mysql_select_db($this->_dbConfig['database'], self::$_connectSource);
mysql_query("set names UTF8", self::$_connectSource);
}
return self::$_connectSource;
}
}
/*$connect = Db::getInstance()->connect();

$sql = "select * from video";
$result = mysql_query($sql, $connect);
echo mysql_num_rows($result);