Pull out elements of an Array that is converted from a XML

im trying to create a php file that can pick out and print values from the code below. This is an XML feed that has been changed to json then to an array. I dont get a choice of how it comes but need to pull out the values from any of the keys but cant seem to get back first array.

I would like to for examples

$key1 = $array['serial'];

This is the array I get given to work with

Array

(
[0] => Array
(
[ns2_ProFeed] => Array
(
[ns2_proFeed] => Array
(
[header] => Array
(
[Id] => 987654321123
[cRef] => 00008797
[prodName] => prod1
[externalRef] => TESTING
)

                        [Identity] => Array
                            (
                                [Serial] => 5654300000214
                                [tel] => +013050000214
                                [ref] => 543365514
                            )

                        [service] => {http://url

                        [responseStatus] => Array
                            (
                                [status] => SUCCESS
                                [timestamp] => 2012-01-09T17:28:02.206+01:00
                            )

                        [parameters] => Array
                            (
                                [parameter] => Array
                                    (
                                        [0] => Array
                                            (
                                                [@attributes] => Array
                                                    (
                                                        [value] => Active
                                                        [name] => Status
                                                    )

                                            )

                                        [1] => Array
                                            (
                                                [@attributes] => Array
                                                    (
                                                        [value] => 2012-01-09 05:25:52.937
                                                        [name] => activationDate
                                                    )

                                            )

                                    )

                            )

                        [options] => Array
                            (
                                [option] => Array
                                    (
                                        [0] => Array
                                            (
                                                [@attributes] => Array
                                                    (
                                                        [startDate] => 2012-01-09T17:27:47.370+01:00
                                                        [value] => on
                                                        [name] => ILC
                                                    )

                                            )

                                        [1] => Array
                                            (
                                                [@attributes] => Array
                                                    (
                                                        [startDate] => 2012-01-09T17:27:47.297+01:00
                                                        [value] => on
                                                        [name] => data
                                                    )

                                            )

                                        [2] => Array
                                            (
                                                [@attributes] => Array
                                                    (
                                                        [startDate] => 2012-01-09T17:27:47.337+01:00
                                                        [value] => on
                                                        [name] => intmessage
                                                    )

                                            )

                                        [3] => Array
                                            (
                                                [@attributes] => Array
                                                    (
                                                        [startDate] => 2012-01-09T17:27:47.323+01:00
                                                        [value] => on
                                                        [name] => multims
                                                    )

                                            )

                                        [4] => Array
                                            (
                                                [@attributes] => Array
                                                    (
                                                        [startDate] => 2012-01-09T17:27:47.280+01:00
                                                        [value] => on
                                                        [name] => simplems
                                                    )

                                            )

                                        [5] => Array
                                            (
                                                [@attributes] => Array
                                                    (
                                                        [startDate] => 2012-01-09T17:27:47.353+01:00
                                                        [value] => on
                                                        [name] => roam
                                                    )

                                            )

                                    )

                            )

                    )

            )

    )

)