XML reader using php

I am building a XML reader to read xml file and insert it into SQL using php

the XML tag look like this

  <f:name>Adam</f:name>

I can acess the information inside it using this

$thePostIdArray[0]

This is not working 100% because some time the order of the XML tags are changed.

I want to access this using code like this

$thePostIdArray[name]

any Ideas ?