PHP class to strip javascripts from html

StripJS.php

<?php

class StripJS {

const JS_ALLOW_HREF = 1;
	const JS_ALLOW_SCRIPT = 2;
	const JS_ALLOW_ATTR_ONX = 4;
	/**
	 * Strips javascript from page. $allowed is bitwise combination of JS_ALLOW_HREF, JS_ALLOW_SCRIPT, JS_ALLOW_ATTR_ONX
	 * 0 - strip everything (no js allowed)
	 * 1 - strip href=...
	 *
	 * @static
	 * @param $html
	 * @param int $allowed
	 * @return mixed
	 */
	static function stripJavascript($html, $allowed = 0)
	{
		if ( ($allowed & self::JS_ALLOW_HREF) == 0) // 1 href=...
		{
			# Totally remove href attribute which starts with javascript:
			$regex = <<<'REGEX'
#href\s*=\s*('|")\s*javascript\s*:.*?\1#is
REGEX;
			$html = preg_replace($regex, '', $html);
		}

		if ( ($allowed & self::JS_ALLOW_SCRIPT) == 0) // 2 <script....
		{
			# First remove self-closing script tags: <script ... />
			$regex = <<<'REGEX'
#<script[^>]+/\s*>#is
REGEX;
			$html = preg_replace($regex, '', $html);

			# Then remove <script...>...</script>
			$regex = <<<'REGEX'
#<script.*?<\s*/\s*script\s*>#is
REGEX;
			$html = preg_replace($regex, '', $html);
		}

		if ( ($allowed & self::JS_ALLOW_ATTR_ONX) == 0) // 4 <tag on.... ---- useful for onlick or onload
		{
			$regex = <<<'REGEX'
#on[^= ]+?=\s*?(['"]).*?\1#is
REGEX;
			$html = preg_replace($regex, '', $html);
		}

		return $html;
	}
}