<?php
class Core{
  /*对数组进行继承*/
  static function inHerit($arr_orgin,$arr_output){
    return array_merge($arr_orgin,$arr_output);
 
  }

  /*打印错误*/
  static function throwError($errmsg){
    echo '<p>error:'.$errmsg.'</p>';
    exit();
  }
}
?>
<?php
class db{
    private $result = array();
    private $connector = array();
    private $configs = array();
    private $active = 0;
    private $default_config = array(
        'dbtype' => 'mysql',
          'index' => 0,'user' => 'root', 'pwd' => '' ,'host' => 'localhost' ,'port'=> 3306,'charset' => 'utf8' ,'dbname' => null
    );
   
   /*初始化*/
   public function __construct($config = array()){
     if($config) $this->connect($config);
   }

   public function __destruct(){
       foreach($this->connector as $index => $connect)
           $this->{'_'.$this->configs[$index]['dbtype'].'_close'}($connect);
           
   }

   private function _mysql_close($connect){
      mysqli_close($connect);
   }
   /*选择连接*/
   public function selectConnect($index){
        return  isset($this->connector[$index]) && (($this->active = $index) || true);
   }
   /*建立连接*/
   public function connect($config){
     (!isset($config['index'])) && $config['index'] = $this->default_config['index']++  ;

     $config = Core::inHerit($this->default_config,$config);
     !in_array($config['dbtype'],array('mysql')) &&  Core::throwError('未支持的数据库类型');
     extract($config);
     $this->configs[$index] = $config;
     $this->{'_'.$config['dbtype'].'_connect'}($user, $pwd,$host,$dbname,$charset,$index,$port);
   
   }
   private function _mysql_connect($user = 'root', $pwd = '' ,$host = 'localhost' ,$dbname = null,$charset = 'utf8' ,$index = 0 ,$port = 3306){
     $this->connector[$index] =  mysqli_connect ( $host, $user, $pwd , null, $port) or Core::throwError(mysql_error());
     $this->active = $index;
     if($dbname) $this->selectDb($dbname,$charset);
   }
  
   /*取得当前连接*/
   private function _getConnect(){
     return $this->connector[$this->active];
   }
   /*取得当前连接使用的数据库类型 带参数自动拼接为函数名*/
   private function _getDbTypeFunc($funcname = null){
     $dbtype = $this->configs[$this->active]['dbtype'];
     return $funcname?'_'.$dbtype.'_'