如何使用SimpleXml访问元素属性?

mon*_*nym 3 php simplexml

我怎样才能在php中访问属性值:

[photos] => SimpleXMLElement Object
    (
        [@attributes] => Array
            (
                [page] => 1
                [pages] => 1
                [perpage] => 24
                [total] => 18
            )
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我尝试过以下方法:

$photos->@attributes['total'] ;
$photos->{'@attributes'}['total'] ;
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以及这方面的许多变化