是否有类似“array_search”的函数用于simplexml对象

I have a codeigniter app that queryies an api and gets a simplexml object. I had hard coded the values I wanted from the simplexml object, but found out later that the structure of the object isn't always the same, so I can't use casting to get the values I need.

Is there an array_search like function that I could use for this so I can use the "classid" to get the value? Here is a sampling of the simplexml object:

    [Package] => SimpleXMLElement Object
    (
        [@attributes] => Array
            (
                [ID] => e981b9a72cd305c7d97cc530ef9b3015
            )

        [Postage] => Array
            (
                [0] => SimpleXMLElement Object
                    (
                        [@attributes] => Array
                            (
                                [CLASSID] => 3
                            )

                        [MailService] => Express Mail<sup>&reg;</sup>
                        [Rate] => 57.60
                    )

                [1] => SimpleXMLElement Object
                    (
                        [@attributes] => Array
                            (
                                [CLASSID] => 2
                            )

                        [MailService] => Express Mail<sup>&reg;</sup> Hold For Pickup
                        [Rate] => 57.60
                    )

                [2] => SimpleXMLElement Object
                    (
                        [@attributes] => Array
                            (
                                [CLASSID] => 55
                            )

                        [MailService] => Express Mail<sup>&reg;</sup> Flat Rate Boxes
                        [Rate] => 39.95
                    )

I was using this to get the [Rate] value:

$usps->Package->Postage[0]->Rate

The problem is I need to use [CLASSID] because that is consistant where the data in the number key(?) changes.