When you google to get a solution to retrieve all the or single tag xml values/attributes you may get approx 10,400,000 results.

Common solution will be to create a module, bring down your own function, bla-bla bla.......

The simplest and statistical way to get is using inbuild drupal functions.

1.  $getXML = drupal_http_request( $url );  //$url is the url to get the xml

2.  To retrieve only single tag.

• $xmlArray = (int)$this->my_xml_parser( $getXML, "</tag>" );

NB: casting can be of any data type as per needed.  "</tag>" is from which tag to retrieve value.  $getXML is from 1.

                                          OR

2. To retrieve all tags in an array.

• $xmlArray= simplexml_load_string( $getXML->data );

NB: This will return all the attributes with array. $getXML->data contains all the xml tags.