error when querying id in Sql table

Question

I have an error when consulting the id in a table, I am developing a system of friendship between users and the error is as follows:

Pdoexception: SQLSTATE[23000]: Integrity Constraint Violation: 1062 Duplicata du Champ '0' pour la clef 'PRIMARY' in C: wamp www sllap php amisade.php on line 14

Behold:

$is_my_friend = DB::getConn()->prepare('SELECT * FROM `friends` WHERE (de=? AND para=?) OR (para=? AND de=?) LIMIT 1');
$is_my_friend->execute(array($idDaSessao,$idExtrangeiro,$idDaSessao,$idExtrangeiro));

if($is_my_friend->rowcount()==0){
   echo'<a class="addFriend" href="php/amisade.php?ac=addfriend&de='.$idDaSessao.'&para='.$idExtrangeiro.'">Adicionar aos amigos</a>';  
}else{
    $astatusfriend = $is_my_friend->fetch(PDO::FETCH_ASSOC);
    if($astatusfriend['status']==0){
       echo'<a class="deleteFriend" href="php/amisade.php?ac=cancel&id='.$astatusfriend['id'].'&de='.$idDaSessao.'&para='.$idExtrangeiro.'">cancelar solicitação enviada</a>';
    }
}

Page amisade.php:

include('../classes/DB.class.php');

if(''<>$_GET['ac']){

   if($_GET['ac']=='addfriend'){

      $is_my_friend = DB::getConn()->prepare('SELECT * FROM `friends` WHERE (de=? AND para=?) OR (para=? AND de=?)');
      $is_my_friend->execute(array($_GET['de'],$_GET['para'],$_GET['de'],$_GET['para']));

      if($is_my_friend->rowCount()==0){

         $addfriend = DB::getConn()->prepare('INSERT INTO `friends` SET `de`=?,`para`=?');
         $addfriend->execute(array($_GET['de'],$_GET['para']));

         header('Location: ../profile.php?uid='.$_GET['para']);
      }
   }
}

if($_GET['ac']=='cancel'){

   $is_my_friend = DB::getConn()->prepare('SELECT * FROM `friends` WHERE (de=? AND para=?)OR(para=? AND de=?) LIMIT 1');
   $is_my_friend->execute(array($_GET['de'],$_GET['para'],$_GET['de'],$_GET['para']));

   if($is_my_friend->rowCount()==1){

      $addfriend = DB::getConn()->prepare('DELETE FROM `friends` WHERE `id`=?');
      $addfriend->execute(array($_GET['id']));

      header('Location: ../profile.php?uid='.$_GET['para']);
   }
}