write a php function to find the first h2 tag inside a php value and insert a div after this tag

function insert_after_h2($content){
  if (is_single()){
    $h2_pos = strpos($content, '<h2>');
    
    if (false !== $h2_pos) {
      $h2_pos +=4;
      $h2_end = strpos($content, '</h2>');
      $h2_len = $h2_end - $h2_pos;
      
      $h2_text = substr($content, $h2_pos, $h2_len);
      $replacement = '<div>' . $h2_text . '</div>';
      
      $content = substr_replace($content, $replacement, $h2_end, 0);
    }
    return $content;
  }
}

add_filter('the_content', 'insert_after_h2');