facebook - can't get $_GET variable in php session_start() script -

i have file called fbconfig.php

if append variable url http://localhost/fbconfig.php?amount=700 cannot retrieve variable in script.

  <?php  session_start(); $amount = $_get['amount']; echo $amount; // nothing happens  // added in v4.0.0 require_once 'autoload.php'; //require 'functions.php'; require 'dbconfig.php'; use facebook\facebooksession; use facebook\facebookredirectloginhelper; use facebook\facebookrequest; use facebook\facebookresponse; use facebook\facebooksdkexception; use facebook\facebookrequestexception; use facebook\facebookauthorizationexception; use facebook\graphobject; use facebook\entities\accesstoken; use facebook\httpclients\facebookcurlhttpclient; use facebook\httpclients\facebookhttpable; // other variables  // init app app id , secret facebooksession::setdefaultapplication( '123123123','12312312' ); // login helper redirect_uri     $helper = new facebookredirectloginhelper('http://localhost/fbconfig.php' ); try {   $session = $helper->getsessionfromredirect(); } catch( facebookrequestexception $ex ) {   // when facebook returns error } catch( exception $ex ) {   // when validation fails or other local issues } // see if have session if ( isset( $session ) ) {   // graph api request user data   $request = new facebookrequest( $session, 'get', '/me' );   $response = $request->execute();   // response   $graphobject = $response->getgraphobject();         $fbid = $graphobject->getproperty('id');              // facebook id         $fbfullname = $graphobject->getproperty('name'); // facebook full name         $fbfirstname = $graphobject->getproperty('first_name'); // facebook full name         $fbsecondname = $graphobject->getproperty('last_name'); // facebook full name         $femail = $graphobject->getproperty('email');    // facebook email id     /* ---- session variables -----*/         $_session['fbid'] = $fbid;                    $_session['fullname'] = $fbfullname;         $_session['email'] = $femail;         $_session['fbfirstname'] =  $fbfirstname;         $_session['fbsecondname'] =  $fbsecondname;   //checkuser($fbid,$fbfullname,$femail,$amount,$days);      /* ---- header location after session ----*/   //header("location: apply.php?amount=".$a."&days=".$b.""); } else {   $loginurl = $helper->getloginurl();  //header("location: ".$loginurl); }  echo $amount; // nothing happens ?> 

so ideas why can't variable? i've tried many different methods

thanks

it's cron job?

* * * * * /path_to_script/fbconfig.php amount=700 

passing $_get parameters cron job