stripAlias

<?php
    function stripAlias($alias) {
        // let add-ons overwrite the default behavior
        $results = $this->invokeEvent('OnStripAlias', array ('alias'=>$alias));
        if (!empty($results)) {
            // if multiple plugins are registered, only the last one is used
            return end($results);
        } else {
            // default behavior: strip invalid characters and replace spaces with dashes.
            $alias = strip_tags($alias); // strip HTML
            $alias = preg_replace('/[^\.A-Za-z0-9 _-]/', '', $alias); // strip non-alphanumeric characters
            $alias = preg_replace('/\s+/', '-', $alias); // convert white-space to dash
            $alias = preg_replace('/-+/', '-', $alias);  // convert multiple dashes to one
            $alias = trim($alias, '-'); // trim excess
            return $alias;
        }
    }

<?php
    function stripAlias($alias, $allowedChars = array()) {
        // let add-ons overwrite the default behavior
        $results = $this->invokeEvent('OnStripAlias', array ('alias'=>$alias));
        if (!empty($results)) {
            // if multiple plugins are registered, only the last one is used
            return end($results);
        } else {
            $allowedChar = (!empty($allowedChars) ? '|\\' . @implode('\\', $allowedChars): '');

            // default behavior: strip invalid characters and replace spaces with dashes.
            $alias = strip_tags($alias); // strip HTML
            $alias = preg_replace('/[^\.A-Za-z0-9 _-'.$allowedChar.']/', '', $alias); // strip non-alphanumeric characters, except any allowed characters
            $alias = preg_replace('/\s+/', '-', $alias); // convert white-space to dash
            $alias = preg_replace('/-+/', '-', $alias);  // convert multiple dashes to one
            $alias = trim($alias, '-'); // trim excess
            return $alias;
        }
    }

<?php

$modx->stripAlias($alias, array('/', '#'));