php把读取xml文档并转换成json数据代码

<?xml version=&#39;1.0&#39; encoding=&#39;utf-8&#39;   
    <root cityid="0" classid="0" placeid="0" yy="0" mm="0" pg="1" ps教程="20" maxPage="1" num="1" serverIP="58.57.65.195"> 
<expo ID="3889" cityid="53" city="北京" classid="0" classname="建筑/装潢/五金" place="中国国际展览中心" placeid="0" tm1="2010-6-3" tm2="2010-6-5" title="20会" Address="北 
里河路13号"> 
<![CDATA[2010北京第十五届中件系列]]> 
</expo> 
</root>

<?php 
$url = "http://www.phprm.com/xml.xml"; 
$dom = new DOMDocument(); 
$dom->load($url); 
$root = $dom->documentElement; 
$arr=array(); 
foreach ($root->childNodes as $item) 
{ 
    if($item->hasChildNodes()) 
    { 
        $tmp=array(); 
        foreach($item->childNodes as $one) 
        { 
            $tmp[$one->tagName]=$one->nodeValue; 
        } 
         
        $arr[$item->tagName]=$tmp; 
    } 
} 
 
$jsonStr = json_encode($arr); 
 
var_dump($jsonStr);