<?php

$arr=array(

    'username'=>'huahua',

    'password'=>'123456',

    'number'=>'15889652911',

);

echo arrayToXml($arr);

function arrayToXml($arr){

    $xml = "<root>";

    foreach ($arr as $key=>$val){

        if(is_array($val)){

            $xml.="<".$key.">".arrayToXml($val)."</".$key.">";

        }else{

            $xml.="<".$key.">".$val."</".$key.">";

        }

    }

    $xml.="</root>";

    //返回xml数据  

    header('Content-type:text/xml;charset=utf-8');

    return $xml;

}

<?php

$xml="<root><username>huahua</username><password>123456</password><number>15889652911</number></root>";

var_dump(xmlToArray($xml));

function xmlToArray($xml){

    //禁止引用外部xml实体

    libxml_disable_entity_loader(true);

    $xmlstring = simplexml_load_string($xml, 'SimpleXMLElement', LIBXML_NOCDATA);

    $val = json_decode(json_encode($xmlstring),true);

    return $val;

}