สอบถามการทำ Facebook Login การทำระบบล็อกอิน (PHP) ด้วยเฟสบุ๊ค และการจัดเก็บลงบน MySQL ช่วยหน่อยคร้า

function Check_fb_login() 
{
 global $cus_fb_token, $cus_fb_id;
 
 if( !isset($cus_fb_token) || $cus_fb_token == "" )
 {
  //check token null
  $json_no_email  = array("status"=>'400',
        "code"=>'MISSING_TOKEN',
        "message"=>'Please provide Token.',
        "data"=>array()
        );
  echo json_encode($json_no_email); 
 }
 else if( !isset($cus_fb_id) || $cus_fb_id == ""  )
 {
  //check facebook id null
  $json_fbid  = array("status"=>'400',
        "code"=>'LOGIN_FAILED',
        "message"=>'INVALID FACEBOOK ID.',
        "data"=>array()
        );
  echo json_encode($json_fbid);       
 }
 else
 { 
  /*Validate facebook token*/
  $fb_data_json = ValidateFacebook($cus_fb_token);
  /*read facebook data*/
  $fb_data  = json_decode($fb_data_json, true);
  echo $fb_data['id']." - ".$cus_fb_id;
  if( $fb_data['id'] != $cus_fb_id )
  {
   $json_profile  = array("status"=>'400',
         "code"=>'INVALID FACEBOOK ID',
         "message"=>'Please provide Facebook valid ID & Token.',
         "data"=>array()
         );
   echo json_encode($json_profile);        
  }
  else /*Valid FACEBOOK ID & token*/
  {
   Login_successful();
  }
 }
}