2015-02-21 08:16:38 +01:00
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<?xml version="1.0" encoding="UTF-8"?>
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<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN"
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"http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
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<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en"><head>
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<meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />
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<meta name="description" content="Explains how to speed up HTML Purifier through caching or inbound filtering." />
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<link rel="stylesheet" type="text/css" href="./style.css" />
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<title>Speeding up HTML Purifier - HTML Purifier</title>
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</head><body>
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<h1 class="subtitled">Speeding up HTML Purifier</h1>
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<div class="subtitle">...also known as the HELP ME LIBRARY IS TOO SLOW MY PAGE TAKE TOO LONG page</div>
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<div id="filing">Filed under End-User</div>
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<div id="index">Return to the <a href="index.html">index</a>.</div>
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<div id="home"><a href="http://htmlpurifier.org/">HTML Purifier</a> End-User Documentation</div>
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<p>HTML Purifier is a very powerful library. But with power comes great
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responsibility, in the form of longer execution times. Remember, this
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library isn't lightly grazing over submitted HTML: it's deconstructing
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the whole thing, rigorously checking the parts, and then putting it back
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together. </p>
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<p>So, if it so turns out that HTML Purifier is kinda too slow for outbound
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filtering, you've got a few options: </p>
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<h2>Inbound filtering</h2>
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<p>Perform filtering of HTML when it's submitted by the user. Since the
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user is already submitting something, an extra half a second tacked on
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to the load time probably isn't going to be that huge of a problem.
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Then, displaying the content is a simple a manner of outputting it
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directly from your database/filesystem. The trouble with this method is
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that your user loses the original text, and when doing edits, will be
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handling the filtered text. While this may be a good thing, especially
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if you're using a WYSIWYG editor, it can also result in data-loss if a
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user makes a typo. </p>
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<p>Example (non-functional):</p>
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<pre><?php
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/**
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* FORM SUBMISSION PAGE
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* display_error($message) : displays nice error page with message
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* display_success() : displays a nice success page
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* display_form() : displays the HTML submission form
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* database_insert($html) : inserts data into database as new row
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*/
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if (!empty($_POST)) {
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require_once '/path/to/library/HTMLPurifier.auto.php';
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require_once 'HTMLPurifier.func.php';
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$dirty_html = isset($_POST['html']) ? $_POST['html'] : false;
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if (!$dirty_html) {
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display_error('You must write some HTML!');
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}
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$html = HTMLPurifier($dirty_html);
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database_insert($html);
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display_success();
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// notice that $dirty_html is *not* saved
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} else {
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display_form();
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}
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?></pre>
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<h2>Caching the filtered output</h2>
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<p>Accept the submitted text and put it unaltered into the database, but
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then also generate a filtered version and stash that in the database.
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Serve the filtered version to readers, and the unaltered version to
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editors. If need be, you can invalidate the cache and have the cached
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filtered version be regenerated on the first page view. Pros? Full data
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retention. Cons? It's more complicated, and opens other editors up to
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XSS if they are using a WYSIWYG editor (to fix that, they'd have to be
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able to get their hands on the *really* original text served in
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plaintext mode). </p>
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<p>Example (non-functional):</p>
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<pre><?php
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/**
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* VIEW PAGE
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* display_error($message) : displays nice error page with message
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* cache_get($id) : retrieves HTML from fast cache (db or file)
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* cache_insert($id, $html) : inserts good HTML into cache system
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* database_get($id) : retrieves raw HTML from database
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*/
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$id = isset($_GET['id']) ? (int) $_GET['id'] : false;
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if (!$id) {
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display_error('Must specify ID.');
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exit;
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}
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$html = cache_get($id); // filesystem or database
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if ($html === false) {
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// cache didn't have the HTML, generate it
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$raw_html = database_get($id);
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require_once '/path/to/library/HTMLPurifier.auto.php';
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require_once 'HTMLPurifier.func.php';
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$html = HTMLPurifier($raw_html);
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cache_insert($id, $html);
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}
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echo $html;
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?></pre>
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<h2>Summary</h2>
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<p>In short, inbound filtering is the simple option and caching is the
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robust option (albeit with bigger storage requirements). </p>
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<p>There is a third option, independent of the two we've discussed: profile
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and optimize HTMLPurifier yourself. Be sure to report back your results
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if you decide to do that! Especially if you port HTML Purifier to C++.
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<tt>;-)</tt></p>
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</body>
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</html>
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<!-- vim: et sw=4 sts=4
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-->
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