Where is Facebook API's get_loggedin_user function

I am using face book API and i have this below code:

include("../src/facebook.php");
// start facebook api with the codes defined in step 1.
//$fb=new Facebook(FB_API_KEY,FB_SECRET);
//$fb_user=$fb->get_loggedin_user();

$facebook = new Facebook(array(
  'appId'  => FB_API_KEY,
  'secret' => FB_SECRET,
  'cookie' => true, 
));

$fb_user=$facebook->get_loggedin_user(); 

BUT.. This function get_loggedin_user() is not available in facebook.php class

Please give me some details about this function. How I can use it.开发者_开发百科

Regards

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this function is available in api file
i dont remember name but file name contains "api" in it
under this folder
../src/