/** 
 * 数组转换成xml 
 * @param $arr 
 * @return string 
 */
function array_to_xml($arr){   
    $xml = '<?xml version="1.0" encoding="UTF-8"?><xml>';    
    foreach ($arr as $key=>$val)    {       
        if (is_numeric($val)){        
            $xml.="<".$key.">".$val."</".$key.">";    
        }else{           
            $xml.="<".$key."><![CDATA[".$val."]]></".$key.">";     
        }   
    }  
    $xml.="</xml>";    
    return $xml;
}