htmlpurifier/INSTALL


Install
    How to install HTML Purifier

HTML Purifier is designed to run out of the box,  so actually using the library
is extremely easy. (Although, if you were looking for a step-by-step
installation GUI, you've come to the wrong place!)  The impatient can scroll
down to the bottom of this INSTALL document to see the code, but you really
should make sure a few things are properly done.


1.  Compatibility

HTML Purifier works in both PHP 4 and PHP 5, from PHP 4.3.9 and up. It has no
core dependencies with other libraries. (Whoopee!)

Optional extensions are iconv (usually installed) and tidy (also common).
If you use UTF-8 and don't plan on pretty-printing HTML, you can get away with
not having either of these extensions.


2.  Including the library

Simply use:

    require_once '/path/to/library/HTMLPurifier.auto.php';

...and you're good to go.  Since HTML Purifier's codebase is fairly
large, I recommend only including HTML Purifier when you need it.

If you don't like your include_path to be fiddled around with, simply set
HTML Purifier's library/ directory to the include path yourself and then:

    require_once 'HTMLPurifier.php';

Only the contents in the library/ folder are necessary, so you can remove
everything else when using HTML Purifier in a production environment.  


3.  Preparing the proper output environment

HTML Purifier is all about web-standards, so accordingly your webpages should
be standards compliant.  HTML Purifier can deal with these doctypes:

* XHTML 1.0 Transitional (default)
* HTML 4.01 Transitional

...and these character encodings:

* UTF-8 (default)
* Any encoding iconv supports (support is crippled for i18n though)

The defaults are there for a reason: they are best-practice choices that
should not be changed lightly.  For those of you in the dark, you can determine
the doctype from this code in your HTML documents:

    <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
        "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">

...and the character encoding from this code:

    <meta http-equiv="Content-type" content="text/html;charset=ENCODING">

For legacy codebases these declarations may be missing.  If that is the case,
STOP, and read up on character encodings and doctypes (in that order).  Here
are some links:

* http://www.joelonsoftware.com/articles/Unicode.html
* http://alistapart.com/stories/doctype/

You may currently be vulnerable to XSS and other security threats, and HTML
Purifier won't be able to fix that.


4. Configuration

HTML Purifier is designed to run out-of-the-box, but occasionally HTML
Purifier needs to be told what to do.  If you answered no to any of these
questions, read on, otherwise, you can skip to the next section (or, if you're
into configuring things just for the heck of it, skip to 4.3).

* Am I using UTF-8?
* Am I using XHTML 1.0 Transitional?

If you answered yes to any of these questions, instantiate a configuration
object and read on:

    $config = HTMLPurifier_Config::createDefault();


4.1. Setting a different character encoding

You really shouldn't use any other encoding except UTF-8, especially if you
plan to support multilingual websites (read section three for more details).
However, switching to UTF-8 is not always immediately feasible, so we can
adapt.

HTML Purifier uses iconv to support other character encodings, as such,
any encoding that iconv supports <http://www.gnu.org/software/libiconv/>
HTML Purifier supports with this code:

    $config->set('Core', 'Encoding', /* put your encoding here */);

An example usage for Latin-1 websites (the most common encoding for English
websites):

    $config->set('Core', 'Encoding', 'ISO-8859-1');

Note that HTML Purifier's support for non-Unicode encodings is crippled by the
fact that any character not supported by that encoding will be silently
dropped, EVEN if it is ampersand escaped.  This is a current limitation of
HTML Purifier that we are NOT actively working to fix.  Patches are welcome,
but there are so many other gotchas and problems in I18N for non-Unicode
encodings that this functionality is low priority.  See
<http://ppewww.ph.gla.ac.uk/~flavell/charset/form-i18n.html> for a more
detailed lowdown on the topic.


4.2. Setting a different doctype

For those of you stuck using HTML 4.01 Transitional, you can disable
XHTML output like this:

    $config->set('Core', 'XHTML', false);

I recommend that you use XHTML, although not as much as I recommend UTF-8.  If
your HTML 4.01 page validates, good for you!

Currently, we can only guarantee transitional-complaint output, future
versions will also allow strict-compliant output.


4.3. Other settings

There are more configuration directives which can be read about
here: <http://hp.jpsband.org/live/configdoc/plain.html>  They're a bit boring,
but they can help out for those of you who like to exert maximum control over
your code.


5.   Using the code

The interface is mind-numbingly simple:

    $purifier = new HTMLPurifier();
    $clean_html = $purifier->purify( $dirty_html );

...or, if you're using the configuration object:

    $purifier = new HTMLPurifier($config);
    $clean_html = $purifier->purify( $dirty_html );

That's it!  For more examples, check out docs/examples/ (they aren't very
different though).  Also, SLOW gives advice on what to do if HTML Purifier
is slowing down your application.


6.   Quick install

If your website is in UTF-8 and XHTML Transitional, use this code:

<?php
    require_once '/path/to/htmlpurifier/library/HTMLPurifier.auto.php';
    
    $purifier = new HTMLPurifier();
    $clean_html = $purifier->purify($dirty_html);
?>

If your website is in a different encoding or doctype, use this code:

<?php
    require_once '/path/to/htmlpurifier/library/HTMLPurifier.auto.php';
    
    $config = HTMLPurifier_Config::createDefault();
    $config->set('Core', 'Encoding', 'ISO-8859-1'); //replace with your encoding
    $config->set('Core', 'XHTML', true); //replace with false if HTML 4.01
    $purifier = new HTMLPurifier($config);
    
    $clean_html = $purifier->purify($dirty_html);
?>