Example of Replacing Tags using PHP

replace-tags.php

<?php
/**
  * Replaces <i> and <b> tags with <em> and <strong> tags.
  * 
  * @param string $string The input string.
  * @return string The filtered text.
  */
function replaceTagsIB($string) {
  $pattern = array('`(<b)([^\w])`i', '`(<i)([^\w])`i');
  $replacement = array("<strong$2", "<em$2");
  $subject = str_replace(array('</b>', '</i>', '</B>', '</I>'), array('</strong>', '</em>', '</strong>', '</em>'), $string);
  return preg_replace($pattern, $replacement, $subject);
}
 
?>