write a joomla function to find the first h2 tag in the content and insert a html content before this tag

function put_stuff_before_h2_tag($content) {
  $html_tag = '<h2>';
  $html_tag_at_position = strpos($content, $html_tag);
  $content_before_tag = substr($content, 0, $html_tag_at_position);
  $content_after_tag = substr($content, $html_tag_at_position);
  $content = $content_before_tag .
    '<div>Stuff I want to put in before the h2 tag</div>' .
    $content_after_tag;
  return $content;
}