一个PHP的String类代码

$s ='中国'; 
$os = new String( $s ); 
echo $os->decode('gbk') ,''; 
echo $os->decode('gbk')->encode('md5'),''; 
 
代码 
 代码如下:

class String extends stdClass 
{ 
private $_val =''; 
public function __construct( $str ='' ) 
{ 
$this->_val = $str; 
} 
public function __toString() 
{ 
return $this->_val; 
} 
public function encode( $coder ) 
{ 
$coder ='encode_' . $coder; 
if( method_exists( $this, $coder ) ) 
{ 
return $this->$coder(); 
}else{ 
return $this; 
} 
} 
public function decode( $coder ) 
{ 
$coder ='decode_' . $coder; 
if( method_exists( $this, $coder ) ) 
{ 
return $this->$coder(); 
}else{ 
return $this; 
} 
} 
private function encode_md5() 
{ 
return new String( md5( $this->_val ) ); 
} 
private function decode_gbk() 
{ 
return new String( iconv('GBK','UTF-8', $this->_val ) ); 
} 
}