＜?php $str = "A 'quote' is ＜b＞bold＜/b＞";  // Outputs: A 'quote' is bold echo htmlentities($str);  // Outputs: A 'quote' is bold echo htmlentities($str, ENT_QUOTES); ?＞ 

function RemoveXSS($val) {  　// remove all non-printable characters. CR(0a) and LF(0b) and TAB(9)  are allowed  　// this prevents some character re-spacing such as ＜java\0script＞  　// note that you have to handle splits with \n, \r, and \t later since they *are* allowed in some inputs  　$val = preg_replace('/([\x00-\x08][\x0b-\x0c][\x0e-\x20])/', '', $val);   　// straight replacements, the user should never need these since they're  normal characters  　// this prevents like ＜IMG SRC=@avascri pt:a& _#X6Cert('XSS')＞  　$search = 'abcdefghijklmnopqrstuvwxyz';  　$search .= 'ABCDEFGHIJKLMNOPQRSTUVWXYZ';  　$search .= '1234567890!@#$%^&*()';  　$search .= '~`";:?+/={}[]-_|\'\\';  　for ($i = 0; $i ＜ strlen($search); $i++) {  // ;? matches the ;, which is optional  // 0{0,7} matches any padded zeros, which are optional and go  up to 8 chars   // @ @ search for the hex values  $val = preg_replace('/(&#[x|X]0{0,8}'.dechex(ord($search[$i])).';?)/i', $search[$i], $val); // with a ;  // @ @ 0{0,7} matches '0' zero to seven times  $val = preg_replace('/(�{0,8}'.ord($search[$i]).';?)/', $search[$i],  $val); // with a ;  　}   　// now the only remaining whitespace attacks are \t, \n, and \r  　$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);   　$found = true; // keep replacing as long as the previous round replaced something  　while ($found == true) {  $val_before = $val;  for ($i = 0; $i ＜ sizeof($ra); $i++) {  　$pattern = '/';  　for ($j = 0; $j ＜ strlen($ra[$i]); $j++) {  if ($j ＞ 0) {  　$pattern .= '(';  　$pattern .= '(&#[x|X]0{0,8}([9][a][b]);?)?';  　$pattern .= '|(�{0,8}([9][10][13]);?)?';  　$pattern .= ')?';  }  　$pattern .= $ra[$i][$j];  }  $pattern .= '/i';  $replacement = substr($ra[$i], 0, 2).'＜x＞'.substr($ra[$i], 2); // add in  ＜＞ to nerf the tag  $val = preg_replace($pattern, $replacement, $val); // filter out the hex tags  if ($val_before == $val) {  　// no replacements were made, so exit the loop  　$found = false;  }  　}  }  }