PHP简单xml解析器对象

嗨，朋友们，我有一个简短的问题，我试着在谷歌上搜索，但找不到任何东西。
下面是反序列化xml对象的打印

SimpleXMLElement Object
(
    [id] => 1234
    [user] => SimpleXMLElement Object
        (
            [id] => 123
            [title] => Mr
            [first-name] => Test
            [last-name] => Test
            [status] => SimpleXMLElement Object
                (
                    [id] => 1
                    [name] => active
                    [type] => user_status
                    [is-enabled] => true
                )
        )
    [start-date] => 2016-02-09T10:27:29.561Z
    [expire-date] => 2016-02-09T11:27:29.561Z
    [auth-token] => 12333423423
)

我如何访问带有-的属性？

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我相信-在PHP变量中不是有效字符

用$obj->{'start-date'}试试吧，谢谢@ChetanAmeta它成功了