如何扩展Prestashop ajaxCall函数来显示tpl文件内容？

I'm facing a problem with extending ajaxCall function located in blocklayered.php

$smarty->assign(
   array(
     'myVariable' => 10,
     'homeSize' => ...,
     'nb_products' => $nb_products,
      ...
));

In my product-list.tpl file i have this

{if isset($myVariable)} 
  {$myVariable}
{/if}

Then when i use blocklayered (choose one of the filter options) page is refreshed by AJAX and show the results with showing 10 that is my myVariable value.

Question is: How to show something else instead of 10 like .tpl file with other contents?

I try also:

$smarty->assign(
   array(
     'myVariable' => $my_variable,
     'homeSize' => ...,
     'nb_products' => $nb_products,
      ...
));

 ...

$my_variable = $smarty->fetch(_PS_THEME_DIR_.'my_content.tpl');

Without success... JSON with myVariable is empty throwing just

" 
    "

You did all good, just in wrong sequence (or show it in wrong sequence). First you need to created variable contains template data and only then use it, like:

$smarty->assign('myVariable', $smarty->fetch(_PS_THEME_DIR_.'my_content.tpl')));

or first $myVariable = ... and then assign it to tpl variable. In this case myVariable will contain content of tpl file. Of course if you want to have some other data transferred from PHP (I mean not just pure html) in my_content.tpl, you need to assign it first, before fetch