<?php
$user = (array)json_decode($user); //user basic info
$shipping_code = '567'; //shipping code
function render($setting, $user, $shipping_code, $products)
{
    //match values like {{$user}}
    $output = preg_replace_callback('~{{(.*?)}}~', function($key) use
    ($user,
    $shipping_code, $products)
    {
      $products = (array)json_decode($products); //products info
      $multiple_products = "";
      foreach($products as $product)
       {
         $multiple_products .= $product->name.'<br/>';//add products in text
       }
      $variable['$products'] = $multiple_products;
      $variable['$user'] =  $user['name'];
      $variable['$shipping_code'] =  $shipping_code;
      return $variable[$key[1]];
      }, $setting);
   return $output;
}
echo $output= render($setting, $user, $shipping_code, $products); //call function
?>