kieranbarnes Independent PHP, WordPress & CubeCart Programmer

Making user inputted data safe

I like to use the PEAR library HTML_Safe to clean up any user input I collect from forms and such before saving to a database. (It is also downloadable seperately from PixelApes).

It strips out any potentially dangerous HTML and code such as;

• opening tag without its closing tag
• closing tag without its opening tag
• any of these tags: “base”, “basefont”, “head”, “html”, “body”, “applet”, “object”,

  “iframe”, “frame”, “frameset”, “script”, “layer”, “ilayer”, “embed”, “bgsound”,
  “link”, “meta”, “style”, “title”, “blink”, “xml” etc.

• any of these attributes: on*, data*, dynsrc
• javascript:/vbscript:/about: etc. protocols
• expression/behavior etc. in styles
• any other active content

It's been stuck at 0.9.9 beta since 2005 but the oldies are the goodies (See qmail, 1 & 2).

Useage, say for example, I want to make the $_GET['show'] variabl, which is passed in the query string safe;

require_once 'HTML/Safe.php';

$safehtml =& new HTML_Safe();
$show_safe = $safehtml->parse($_GET['show']);

For a lazy simple programmer it is simple to use even with ADODb's AutoExecute() function which I am using more and more recently;

$safehtml =& new HTML_Safe();

foreach ($_POST as $foo) {
$_POST[$foo] = $safehtml->parse($foo);
}

$insert_rs = $conn->AutoExecute('SOME_TABLE', $_POST, 'INSERT');

Simple as.

It is also worth looking at HTMLPurifer which seems to be more recently updated.