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413 lines
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HTML
413 lines
15 KiB
HTML
<?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">
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<head>
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<meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />
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<meta name="description" content="Describes config schema framework in HTML Purifier." />
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<link rel="stylesheet" type="text/css" href="./style.css" />
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<title>Config Schema - HTML Purifier</title>
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</head>
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<body>
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<h1>Config Schema</h1>
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<div id="filing">Filed under Development</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>
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HTML Purifier has a fairly complex system for configuration. Users
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interact with a <code>HTMLPurifier_Config</code> object to
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set configuration directives. The values they set are validated according
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to a configuration schema, <code>HTMLPurifier_ConfigSchema</code>.
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</p>
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<p>
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The schema is mostly transparent to end-users, but if you're doing development
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work for HTML Purifier and need to define a new configuration directive,
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you'll need to interact with it. We'll also talk about how to define
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userspace configuration directives at the very end.
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</p>
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<h2>Write a directive file</h2>
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<p>
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Directive files define configuration directives to be used by
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HTML Purifier. They are placed in <code>library/HTMLPurifier/ConfigSchema/schema/</code>
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in the form <code><em>Namespace</em>.<em>Directive</em>.txt</code> (I
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couldn't think of a more descriptive file extension.)
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Directive files are actually what we call <code>StringHash</code>es,
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i.e. associative arrays represented in a string form reminiscent of
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<a href="http://qa.php.net/write-test.php">PHPT</a> tests. Here's a
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sample directive file, <code>Test.Sample.txt</code>:
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</p>
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<pre>Test.Sample
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TYPE: string/null
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DEFAULT: NULL
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ALLOWED: 'foo', 'bar'
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VALUE-ALIASES: 'baz' => 'bar'
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VERSION: 3.1.0
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--DESCRIPTION--
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This is a sample configuration directive for the purposes of the
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<code>dev-config-schema.html<code> documentation.
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--ALIASES--
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Test.Example</pre>
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<p>
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Each of these segments has a specific meaning:
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</p>
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<table class="table">
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<thead>
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<tr>
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<th>Key</th>
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<th>Example</th>
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<th>Description</th>
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</tr>
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</thead>
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<tbody>
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<tr>
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<td>ID</td>
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<td>Test.Sample</td>
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<td>The name of the directive, in the form Namespace.Directive
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(implicitly the first line)</td>
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</tr>
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<tr>
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<td>TYPE</td>
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<td>string/null</td>
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<td>The type of variable this directive accepts. See below for
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details. You can also add <code>/null</code> to the end of
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any basic type to allow null values too.</td>
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</tr>
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<tr>
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<td>DEFAULT</td>
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<td>NULL</td>
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<td>A parseable PHP expression of the default value.</td>
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</tr>
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<tr>
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<td>DESCRIPTION</td>
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<td>This is a...</td>
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<td>An HTML description of what this directive does.</td>
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</tr>
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<tr>
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<td>VERSION</td>
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<td>3.1.0</td>
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<td><em>Recommended</em>. The version of HTML Purifier this directive was added.
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Directives that have been around since 1.0.0 don't have this,
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but any new ones should.</td>
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</tr>
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<tr>
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<td>ALIASES</td>
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<td>Test.Example</td>
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<td><em>Optional</em>. A comma separated list of aliases for this directive.
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This is most useful for backwards compatibility and should
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not be used otherwise.</td>
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</tr>
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<tr>
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<td>ALLOWED</td>
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<td>'foo', 'bar'</td>
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<td><em>Optional</em>. Set of allowed value for a directive,
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a comma separated list of parseable PHP expressions. This
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is only allowed string, istring, text and itext TYPEs.</td>
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</tr>
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<tr>
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<td>VALUE-ALIASES</td>
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<td>'baz' => 'bar'</td>
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<td><em>Optional</em>. Mapping of one value to another, and
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should be a comma separated list of keypair duples. This
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is only allowed string, istring, text and itext TYPEs.</td>
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</tr>
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<tr>
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<td>DEPRECATED-VERSION</td>
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<td>3.1.0</td>
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<td><em>Not shown</em>. Indicates that the directive was
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deprecated this version.</td>
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</tr>
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<tr>
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<td>DEPRECATED-USE</td>
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<td>Test.NewDirective</td>
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<td><em>Not shown</em>. Indicates what new directive should be
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used instead. Note that the directives will functionally be
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different, although they should offer the same functionality.
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If they are identical, use an alias instead.</td>
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</tr>
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<tr>
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<td>EXTERNAL</td>
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<td>CSSTidy</td>
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<td><em>Not shown</em>. Indicates if there is an external library
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the user will need to download and install to use this configuration
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directive. As of right now, this is merely a Google-able name; future
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versions may also provide links and instructions.</td>
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</tr>
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</tbody>
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</table>
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<p>
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Some notes on format and style:
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</p>
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<ul>
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<li>
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Each of these keys can be expressed in the short format
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(<code>KEY: Value</code>) or the long format
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(<code>--KEY--</code> with value beneath). You must use the
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long format if multiple lines are needed, or if a long format
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has been used already (that's why <code>ALIASES</code> in our
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example is in the long format); otherwise, it's user preference.
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</li>
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<li>
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The HTML descriptions should be wrapped at about 80 columns; do
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not rely on editor word-wrapping.
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</li>
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</ul>
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<p>
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Also, as promised, here is the set of possible types:
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</p>
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<table class="table">
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<thead>
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<tr>
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<th>Type</th>
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<th>Example</th>
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<th>Description</th>
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</tr>
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</thead>
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<tbody>
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<tr>
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<td>string</td>
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<td>'Foo'</td>
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<td><a href="http://docs.php.net/manual/en/language.types.string.php">String</a> without newlines</td>
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</tr>
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<tr>
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<td>istring</td>
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<td>'foo'</td>
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<td>Case insensitive ASCII string without newlines</td>
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</tr>
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<tr>
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<td>text</td>
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<td>"A<em>\n</em>b"</td>
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<td>String with newlines</td>
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</tr>
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<tr>
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<td>itext</td>
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<td>"a<em>\n</em>b"</td>
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<td>Case insensitive ASCII string without newlines</td>
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</tr>
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<tr>
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<td>int</td>
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<td>23</td>
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<td>Integer</td>
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</tr>
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<tr>
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<td>float</td>
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<td>3.0</td>
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<td>Floating point number</td>
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</tr>
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<tr>
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<td>bool</td>
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<td>true</td>
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<td>Boolean</td>
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</tr>
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<tr>
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<td>lookup</td>
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<td>array('key' => true)</td>
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<td>Lookup array, used with <code>isset($var[$key])</code></td>
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</tr>
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<tr>
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<td>list</td>
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<td>array('f', 'b')</td>
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<td>List array, with ordered numerical indexes</td>
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</tr>
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<tr>
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<td>hash</td>
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<td>array('key' => 'val')</td>
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<td>Associative array of keys to values</td>
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</tr>
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<tr>
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<td>mixed</td>
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<td>new stdclass</td>
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<td>Any PHP variable is fine</td>
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</tr>
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</tbody>
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</table>
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<p>
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The examples represent what will be returned out of the configuration
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object; users have a little bit of leeway when setting configuration
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values (for example, a lookup value can be specified as a list;
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HTML Purifier will flip it as necessary.) These types are defined
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in <a href="http://repo.or.cz/w/htmlpurifier.git?a=blob;hb=HEAD;f=library/HTMLPurifier/VarParser.php">
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library/HTMLPurifier/VarParser.php</a>.
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</p>
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<p>
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For more information on what values are allowed, and how they are parsed,
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consult <a href="http://repo.or.cz/w/htmlpurifier.git?a=blob;hb=HEAD;f=library/HTMLPurifier/ConfigSchema/InterchangeBuilder.php">
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library/HTMLPurifier/ConfigSchema/InterchangeBuilder.php</a>, as well
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as <a href="http://repo.or.cz/w/htmlpurifier.git?a=blob;hb=HEAD;f=library/HTMLPurifier/ConfigSchema/Interchange/Directive.php">
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library/HTMLPurifier/ConfigSchema/Interchange/Directive.php</a> for
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the semantics of the parsed values.
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</p>
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<h2>Refreshing the cache</h2>
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<p>
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You may have noticed that your directive file isn't doing anything
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yet. That's because it hasn't been added to the runtime
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<code>HTMLPurifier_ConfigSchema</code> instance. Run
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<code>maintenance/generate-schema-cache.php</code> to fix this.
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If there were no errors, you're good to go! Don't forget to add
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some unit tests for your functionality!
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</p>
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<p>
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If you ever make changes to your configuration directives, you
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will need to run this script again.
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</p>
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<h2>Adding in-house schema definitions</h2>
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<p>
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Placing stuff directly in HTML Purifier's source tree is generally not a
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good idea, so HTML Purifier 4.0.0+ has some facilities in place to make your
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life easier.
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</p>
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<p>
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The first is to pass an extra parameter to <code>maintenance/generate-schema-cache.php</code>
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with the location of your directory (relative or absolute path will do). For example,
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if I'm storing my custom definitions in <em>/var/htmlpurifier/myschema</em>, run:
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<code>php maintenance/generate-schema-cache.php /var/htmlpurifier/myschema</code>.
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</p>
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<p>
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Alternatively, you can create a small loader PHP file in the HTML Purifier base
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directory named <code>config-schema.php</code> (this is the same directory
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you would place a <code>test-settings.php</code> file). In this file, add
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the following line for each directory you want to load:
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</p>
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<pre>$builder->buildDir($interchange, '/var/htmlpurifier/myschema');</pre>
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<p>You can even load a single file using:</p>
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<pre>$builder->buildFile($interchange, '/var/htmlpurifier/myschema/MyApp.Directive.txt');</pre>
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<p>Storing custom definitions that you don't plan on sending back upstream in
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a separate directory is <em>definitely</em> a good idea! Additionally, picking
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a good namespace can go a long way to saving you grief if you want to use
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someone else's change, but they picked the same name, or if HTML Purifier
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decides to add support for a configuration directive that has the same name.</p>
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<!-- TODO: how to name directives that rely on naming conventions -->
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<h2>Errors</h2>
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<p>
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All directive files go through a rigorous validation process
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through <a href="http://repo.or.cz/w/htmlpurifier.git?a=blob;hb=HEAD;f=library/HTMLPurifier/ConfigSchema/Validator.php">
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library/HTMLPurifier/ConfigSchema/Validator.php</a>, as well
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as some basic checks during building. While
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listing every error out here is out-of-scope for this document, we
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can give some general tips for interpreting error messages.
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There are two types of errors: builder errors and validation errors.
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</p>
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<h3>Builder errors</h3>
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<blockquote>
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<p>
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<strong>Exception:</strong> Expected type string, got
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integer in DEFAULT in directive hash 'Ns.Dir'
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</p>
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</blockquote>
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<p>
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You can identify a builder error by the keyword "directive hash."
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These are the easiest to deal with, because they directly correspond
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with your directive file. Find the offending directive file (which
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is the directive hash plus the .txt extension), find the
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offending index ("in DEFAULT" means the DEFAULT key) and fix the error.
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This particular error would occur if your default value is not the same
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type as TYPE.
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</p>
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<h3>Validation errors</h3>
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<blockquote>
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<p>
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<strong>Exception:</strong> Alias 3 in valueAliases in directive
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'Ns.Dir' must be a string
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</p>
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</blockquote>
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<p>
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These are a little trickier, because we're not actually validating
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your directive file, or even the direct string hash representation.
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We're validating an Interchange object, and the error messages do
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not mention any string hash keys.
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</p>
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<p>
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Nevertheless, it's not difficult to figure out what went wrong.
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Read the "context" statements in reverse:
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</p>
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<dl>
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<dt>in directive 'Ns.Dir'</dt>
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<dd>This means we need to look at the directive file <code>Ns.Dir.txt</code></dd>
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<dt>in valueAliases</dt>
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<dd>There's no key actually called this, but there's one that's close:
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VALUE-ALIASES. Indeed, that's where to look.</dd>
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<dt>Alias 3</dt>
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<dd>The value alias that is equal to 3 is the culprit.</dd>
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</dl>
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<p>
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In this particular case, you're not allowed to alias integers values to
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strings values.
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</p>
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<p>
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The most difficult part is translating the Interchange member variable (valueAliases)
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into a directive file key (VALUE-ALIASES), but there's a one-to-one
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correspondence currently. If the two formats diverge, any discrepancies
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will be described in <a href="http://repo.or.cz/w/htmlpurifier.git?a=blob;hb=HEAD;f=library/HTMLPurifier/ConfigSchema/InterchangeBuilder.php">
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library/HTMLPurifier/ConfigSchema/InterchangeBuilder.php</a>.
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</p>
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<h2>Internals</h2>
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<p>
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Much of the configuration schema framework's codebase deals with
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shuffling data from one format to another, and doing validation on this
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data.
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The keystone of all of this is the <code>HTMLPurifier_ConfigSchema_Interchange</code>
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class, which represents the purest, parsed representation of the schema.
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</p>
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<p>
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Hand-writing this data is unwieldy, however, so we write directive files.
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These directive files are parsed by <code>HTMLPurifier_StringHashParser</code>
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into <code>HTMLPurifier_StringHash</code>es, which then
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are run through <code>HTMLPurifier_ConfigSchema_InterchangeBuilder</code>
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to construct the interchange object.
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</p>
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<p>
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From the interchange object, the data can be siphoned into other forms
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using <code>HTMLPurifier_ConfigSchema_Builder</code> subclasses.
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For example, <code>HTMLPurifier_ConfigSchema_Builder_ConfigSchema</code>
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generates a runtime <code>HTMLPurifier_ConfigSchema</code> object,
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which <code>HTMLPurifier_Config</code> uses to validate its incoming
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data. There is also an XML serializer, which is used to build documentation.
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</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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