单例模式有三大原则：
构造函数不能为public
有一个保存实例的静态成员变量
拥有访问这个实例的公共静态方法
基于单例模式的php数据库连接类:
class Db{
static private $_instance;
static private $_connectSource;
private $_dbConfig = array(
'host' => '127.0.0.1',
'user' => 'root',
'password' => 'root',
'database' =>'数据库名',
);
private function __construct(){
}
static public function getInstance(){
if(!(self::$_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){
die('mysql error'.mysql_error());
}
mysql_select_db($this->_dbConfig['database'],self::$_connectSource);
mysql_query("set names UTF8",self::$_connectSource);
}
return self::$_connectSource;
}
}
使用的时候直接实例化就可以：比如：
$connect = Db::getInstance()->connect();
内有有参考《php接口开发》视频教程