Use handlebars-like syntax and do template rendering with associative arrays, where the key is var name, and the value is the rendered content.

assoc_replace.php

<?php
function assoc_replace ($templateStr, $replacementList) {
  $searchStrings = [];
  $replacements  = [];
  foreach ($replacementList as $key => $val) {
    array_push($searchStrings, '{{'.$key.'}}');
    array_push($replacements, $val);
  }
  return str_replace($searchStrings, $replacements, $templateStr);
}