MODX Output Modifier that parses the $input value into the $options value.

snippet.wrap.php

<?php
/**
 * Wraps the value of a placeholder.
 * [[*introtext:wrap=`<p class="intro">|</p>`]]
 */
return (empty($input) === false && strpos($options, '|') !== false) ? str_replace('|', $input, $options) : '';