php 怎么取组里的值

[holinhot]

Array
(
[list-instancesresponse] => Array
(
[requestid] => 0FA02641-0DE4-DB43-EEA0-10BCCF0E987A
[instancesSet] => Array
(
[item] => Array
(
[cu_id] => 71993
[vm_status] => RUNNING
[vm_ip_address] => 10.10.10.102
[vm_created_date] => 1456249087
[rate_per_hr] => 0.0068
[vm_image] => ubuntu-14.04_64bit
[vm_name] => 102
[vm_image_display_name] => Ubuntu 14.04 LTS Server 64-Bit
[vm_ram_req] => 512
[vm_cpu_req] => 1
[vm_disk_req] => 20
[vm_network_req] => 1
[vm_bandwidth] => 600
[vm_os_architecture] => 64
[vm_plan_name] => XS
[vm_description] => test1
[InstanceId] => 102
)

[1item] => Array
                    (
                        [cu_id] => 71993
                        [vm_status] => RUNNING
                        [vm_ip_address] => 10.10.10.102
                        [vm_created_date] => 1456248612
                        [rate_per_hr] => 0.0068
                        [vm_image] => ubuntu-14.04_64bit
                        [vm_name] => 103
                        [vm_image_display_name] => Ubuntu 14.04 LTS Server 64-Bit
                        [vm_ram_req] => 512
                        [vm_cpu_req] => 1
                        [vm_disk_req] => 20
                        [vm_network_req] => 1
                        [vm_bandwidth] => 600
                        [vm_os_architecture] => 64
                        [vm_plan_name] => XS
                        [vm_description] => test2
                        [InstanceId] => 103
                    )




            )

    )

[Timestamp] => 1456250161

)

比如取里面的 ip
vm_ip_address