防止xss攻击

<?php
function _removeXSS($val) {
    $search = 'abcdefghijklmnopqrstuvwxyz';
    $search .= 'ABCDEFGHIJKLMNOPQRSTUVWXYZ';
    $search .= '1234567890!@#$%^&*()';
    $search .= '~`";:?+/={}[]-_|\'\\';
    for($i = 0; $i < strlen ( $search ); $i ++)
    {
        $val = preg_replace( '/(&#[xX]0{0,8}' . dechex(ord( $search [$i])) . ';?)/i', $search[$i], $val);
        $val = preg_replace( '/(&#0{0,8}' . ord($search[$i]) . ';?)/', $search[$i], $val);
    }

    $ra1 = array('javascript','vbscript','expression','applet','meta','xml','blink','link','style','script','embed','object','iframe','frame','frameset','ilayer','layer','bgsound','title','base' );
    $ra2 = array('onabort','onactivate','onafterprint','onafterupdate','onbeforeactivate','onbeforecopy','onbeforecut','onbeforedeactivate','onbeforeeditfocus','onbeforepaste','onbeforeprint','onbeforeunload','onbeforeupdate','onblur','onbounce','oncellchange','onchange','onclick','oncontextmenu','oncontrolselect',    'oncopy',    'oncut','ondataavailable','ondatasetchanged','ondatasetcomplete','ondblclick','ondeactivate','ondrag','ondragend','ondragenter','ondragleave','ondragover','ondragstart','ondrop','onerror','onerrorupdate','onfilterchange','onfinish','onfocus','onfocusin','onfocusout','onhelp','onkeydown','onkeypress','onkeyup','onlayoutcomplete','onload','onlosecapture','onmousedown','onmouseenter','onmouseleave','onmousemove','onmouseout','onmouseover','onmouseup','onmousewheel','onmove','onmoveend','onmovestart','onpaste','onpropertychange','onreadystatechange','onreset','onresize','onresizeend','onresizestart','onrowenter','onrowexit','onrowsdelete','onrowsinserted','onscroll','onselect','onselectionchange','onselectstart','onstart','onstop','onsubmit', 'onunload' );
    $ra = array_merge($ra1, $ra2);

    $found = true;
    while ($found == true)
    {
        $valBefore = $val;
        for($i = 0; $i < sizeof ($ra); $i ++)
        {
            $pattern = '/';
            for($j = 0; $j < strlen($ra[$i]); $j ++)
            {
                if ($j > 0)
                {
                    $pattern .= '(';
                    $pattern .= '(&#[xX]0{0,8}([9ab]);)';
                    $pattern .= '|';
                    $pattern .= '|(&#0{0,8}([9|10|13]);)';
                    $pattern .= ')*';
                }
                $pattern .= $ra[$i][$j];
            }
            $pattern .= '/i';
            $replacement = substr($ra[$i], 0, 2) . '<x>' . substr($ra[$i], 2);
            $val = preg_replace($pattern, $replacement, $val);
            if ($valBefore == $val)
            {
                $found = false;
            }
        }
    }
    return $val;
}

echo _removeXSS ( "<ef10000><script language='javascript'>alert('hello world');</script>" );
?>