php curl 寫在同一個function但沒辦法同時兩次請求？

我把curl寫在一個function像這樣：

function httpRequest ($api, $data_string)
{
  $ch = curl_init($api);
  curl_setopt($ch, CURLOPT_POST, 1);
  curl_setopt($ch, CURLOPT_CUSTOMREQUEST, "POST");
  curl_setopt($ch, CURLOPT_POSTFIELDS, $data_string);
  curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
  curl_setopt($ch, CURLOPT_HTTPHEADER, array('Content-Type: application/json'));
  $result = curl_exec($ch);
  curl_close($ch);

  return json_decode($result);
}

然後我同一頁有兩隻請求

$api_a = 'a';
$api_b = 'b';

$get_a = array(
      "session" => $_SESSION['session']
    );
    $get_a_str = json_encode($get_a);
    $get_a = httpRequest($api_a, $get_a_str);
    
$get_b = array(
      "session" => $_SESSION['session']
    );
    $get_b_str = json_encode($get_b);
    $get_b = httpRequest($api_b, $get_b_str);

寫在同一頁：

  <?foreach ($get_a->dataA as $key) {?>
          <?=@$key->{'name'};?>
        <?}?>
  <?foreach ($get_b->dataB as $key) {?>
          <?=@$key->{'name'};?>
        <?}?>

為什麼這樣不行同時呢？
他只能請求其中一個，另一個會無效？（誰在最上面誰才能運行）

他會抱錯：

Undefined variable: get_b
Trying to get property 'dataB' of non-object
Invalid argument supplied for foreach()

我只要把Ａ刪掉就可以運行Ｂ
把Ｂ刪掉就可以運行Ａ