PHP如何将XML字符串转数组？

$obj = simplexml_load_string($str,"SimpleXMLElement", LIBXML_NOCDATA);

$json_str = json_encode($obj);

$xml_arr = json_decode($json_str, true);

$str = '<xml>
    <ToUserName> <![CDATA[gh_fc0a06a20993]]> </ToUserName>
    <FromUserName> <![CDATA[oZI8Fj040-be6rlDohc6gkoPOQTQ]]> </FromUserName>
    <CreateTime>1472549042</CreateTime>
    <MsgType> <![CDATA[event]]> </MsgType>
    <Event> <![CDATA[user_consume_card]]> </Event>
    <CardId> <![CDATA[pZI8Fj8y-E8hpvho2d1ZvpGwQBvA]]> </CardId>
    <UserCardCode> <![CDATA[452998530302]]> </UserCardCode>
    <ConsumeSource> <![CDATA[FROM_API]]> </ConsumeSource>
    <LocationName> <![CDATA[]]> </LocationName>
    <StaffOpenId> <![CDATA[oZ********nJ3bPJu_Rtjkw4c]]> </StaffOpenId>
    <VerifyCode> <![CDATA[]]> </VerifyCode>
    <RemarkAmount> <![CDATA[]]> </RemarkAmount>
    <OuterStr> <![CDATA[xxxxx]]> </OuterStr>
</xml>';

$obj = simplexml_load_string($str,"SimpleXMLElement", LIBXML_NOCDATA);
$test = json_decode(json_encode($obj),true);
$arr = [
    'FromUserName' => $test['FromUserName'],
    'ToUserName' => $test['ToUserName'],
    'CreateTime' => $test['CreateTime'],
    'CardId' => $test['CardId'],
    'UserCardCode' => $test['UserCardCode'],
    'ConsumeSource' => $test['ConsumeSource'],
    'StaffOpenId' => $test['StaffOpenId']
];
$arr = array_map('trim',$arr);
var_dump($arr);