解决了 

public static function xmlToEncode($data){

$xml="";

foreach($data as $key=>$value){

$arr="";

if(is_numeric($key){

$arr.="<item>";

}

$xml.="<{$key}>";

//$xml.=$value这样写就会报错误，改成下面

$xml.=is_array($value)?self::xmlToEncode($value):$value;

$xml.="</{$key}>\n";

}

我也是这个问题

This page contains the following errors:

error on line 2 at column 1: Extra content at the end of the document

Below is a rendering of the page up to the first error.

怎么解决的

已解决，发完问题才看到优化后的代码！谢谢老师！