php - How to retrieve PID of a photo? -

$pid = $fb->api(array(          'method' => 'fql.query',          'query' => 'select first_name user uid='.$session['uid'])     );    try {      $fb->api( array(         'method' => 'photos.addtag',          'pid'   => $pid[0],          'tag_uid' => '100000492080016',         'tag_text' => "hello",         'x' => 65,          'y' => 65,      ) ); } catch (facebookapiexception $e) {     print_r($e); } 

when use above code in facebook app, shows error

param pid must valid merged photo id.

how can resolve problem? or can explain how retrieve pid of pic in other way?

in query select first_name user uid='.$session['uid'] retriving first_name database, thats problem think.

so think need change query.

select first_name,pid user uid='.$session['uid'] 

i not familiar facebook apis , might m true.

thanks.