1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
|
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en"><head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />
<meta name="description" content="Tutorial for customizing HTML Purifier's tag and attribute sets." />
<link rel="stylesheet" type="text/css" href="style.css" />
<title>Customize - HTML Purifier</title>
</head><body>
<h1 class="subtitled">Customize!</h1>
<div class="subtitle">HTML Purifier is a Swiss-Army Knife</div>
<div id="filing">Filed under End-User</div>
<div id="index">Return to the <a href="index.html">index</a>.</div>
<div id="home"><a href="http://htmlpurifier.org/">HTML Purifier</a> End-User Documentation</div>
<p>
HTML Purifier has this quirk where if you try to allow certain elements or
attributes, HTML Purifier will tell you that it's not supported, and that
you should go to the forums to find out how to implement it. Well, this
document is how to implement elements and attributes which HTML Purifier
doesn't support out of the box.
</p>
<h2>Is it necessary?</h2>
<p>
Before we even write any code, it is paramount to consider whether or
not the code we're writing is necessary or not. HTML Purifier, by default,
contains a large set of elements and attributes: large enough so that
<em>any</em> element or attribute in XHTML 1.0 or 1.1 (and its HTML variants)
that can be safely used by the general public is implemented.
</p>
<p>
So what needs to be implemented? (Feel free to skip this section if
you know what you want).
</p>
<h3>XHTML 1.0</h3>
<p>
All of the modules listed below are based off of the
<a href="http://www.w3.org/TR/2001/REC-xhtml-modularization-20010410/abstract_modules.html#sec_5.2.">modularization of
XHTML</a>, which, while technically for XHTML 1.1, is quite a useful
resource.
</p>
<ul>
<li>Structure</li>
<li>Frames</li>
<li>Applets (deprecated)</li>
<li>Forms</li>
<li>Image maps</li>
<li>Objects</li>
<li>Frames</li>
<li>Events</li>
<li>Meta-information</li>
<li>Style sheets</li>
<li>Link (not hypertext)</li>
<li>Base</li>
<li>Name</li>
</ul>
<p>
If you don't recognize it, you probably don't need it. But the curious
can look all of these modules up in the above-mentioned document. Note
that inline scripting comes packaged with HTML Purifier (more on this
later).
</p>
<h3>XHTML 1.1</h3>
<p>
As of HTMLPurifier 2.1.0, we have implemented the
<a href="http://www.w3.org/TR/2001/REC-ruby-20010531/">Ruby module</a>,
which defines a set of tags
for publishing short annotations for text, used mostly in Japanese
and Chinese school texts, but applicable for positioning any text (not
limited to translations) above or below other corresponding text.
</p>
<h3>HTML 5</h3>
<p>
<a href="http://www.whatwg.org/specs/web-apps/current-work/">HTML 5</a>
is a fork of HTML 4.01 by WHATWG, who believed that XHTML 2.0 was headed
in the wrong direction. It too is a working draft, and may change
drastically before publication, but it should be noted that the
<code>canvas</code> tag has been implemented by many browser vendors.
</p>
<h3>Proprietary</h3>
<p>
There are a number of proprietary tags still in the wild. Many of them
have been documented in <a href="ref-proprietary-tags.txt">ref-proprietary-tags.txt</a>,
but there is currently no implementation for any of them.
</p>
<h3>Extensions</h3>
<p>
There are also a number of other XML languages out there that can
be embedded in HTML documents: two of the most popular are MathML and
SVG, and I frequently get requests to implement these. But they are
expansive, comprehensive specifications, and it would take far too long
to implement them <em>correctly</em> (most systems I've seen go as far
as whitelisting tags and no further; come on, what about nesting!)
</p>
<p>
Word of warning: HTML Purifier is currently <em>not</em> namespace
aware.
</p>
<h2>Giving back</h2>
<p>
As you may imagine from the details above (don't be abashed if you didn't
read it all: a glance over would have done), there's quite a bit that
HTML Purifier doesn't implement. Recent architectural changes have
allowed HTML Purifier to implement elements and attributes that are not
safe! Don't worry, they won't be activated unless you set %HTML.Trusted
to true, but they certainly help out users who need to put, say, forms
on their page and don't want to go through the trouble of reading this
and implementing it themself.
</p>
<p>
So any of the above that you implement for your own application could
help out some other poor sap on the other side of the globe. Help us
out, and send back code so that it can be hammered into a module and
released with the core. Any code would be greatly appreciated!
</p>
<h2>And now...</h2>
<p>
Enough philosophical talk, time for some code:
</p>
<pre>$config = HTMLPurifier_Config::createDefault();
$config->set('HTML.DefinitionID', 'enduser-customize.html tutorial');
$config->set('HTML.DefinitionRev', 1);
if ($def = $config->maybeGetRawHTMLDefinition()) {
// our code will go here
}</pre>
<p>
Assuming that HTML Purifier has already been properly loaded (hint:
include <code>HTMLPurifier.auto.php</code>), this code will set up
the environment that you need to start customizing the HTML definition.
What's going on?
</p>
<ul>
<li>
The first three lines are regular configuration code:
<ul>
<li>
%HTML.DefinitionID is set to a unique identifier for your
custom HTML definition. This prevents it from clobbering
other custom definitions on the same installation.
</li>
<li>
%HTML.DefinitionRev is a revision integer of your HTML
definition. Because HTML definitions are cached, you'll need
to increment this whenever you make a change in order to flush
the cache.
</li>
</ul>
</li>
<li>
The fourth line retrieves a raw <code>HTMLPurifier_HTMLDefinition</code>
object that we will be tweaking. Interestingly enough, we have
placed it in an if block: this is because
<code>maybeGetRawHTMLDefinition</code>, as its name suggests, may
return a NULL, in which case we should skip doing any
initialization. This, in fact, will correspond to when our fully
customized object is already in the cache.
</li>
</ul>
<h2>Turn off caching</h2>
<p>
To make development easier, we're going to temporarily turn off
definition caching:
</p>
<pre>$config = HTMLPurifier_Config::createDefault();
$config->set('HTML.DefinitionID', 'enduser-customize.html tutorial');
$config->set('HTML.DefinitionRev', 1);
<strong>$config->set('Cache.DefinitionImpl', null); // TODO: remove this later!</strong>
$def = $config->getHTMLDefinition(true);</pre>
<p>
A few things should be mentioned about the caching mechanism before
we move on. For performance reasons, HTML Purifier caches generated
<code>HTMLPurifier_Definition</code> objects in serialized files
stored (by default) in <code>library/HTMLPurifier/DefinitionCache/Serializer</code>.
A lot of processing is done in order to create these objects, so it
makes little sense to repeat the same processing over and over again
whenever HTML Purifier is called.
</p>
<p>
In order to identify a cache entry, HTML Purifier uses three variables:
the library's version number, the value of %HTML.DefinitionRev and
a serial of relevant configuration. Whenever any of these changes,
a new HTML definition is generated. Notice that there is no way
for the definition object to track changes to customizations: here, it
is up to you to supply appropriate information to DefinitionID and
DefinitionRev.
</p>
<h2 id="addAttribute">Add an attribute</h2>
<p>
For this example, we're going to implement the <code>target</code> attribute found
on <code>a</code> elements. To implement an attribute, we have to
ask a few questions:
</p>
<ol>
<li>What element is it found on?</li>
<li>What is its name?</li>
<li>Is it required or optional?</li>
<li>What are valid values for it?</li>
</ol>
<p>
The first three are easy: the element is <code>a</code>, the attribute
is <code>target</code>, and it is not a required attribute. (If it
was required, we'd need to append an asterisk to the attribute name,
you'll see an example of this in the addElement() example).
</p>
<p>
The last question is a little trickier.
Lets allow the special values: _blank, _self, _target and _top.
The form of this is called an <strong>enumeration</strong>, a list of
valid values, although only one can be used at a time. To translate
this into code form, we write:
</p>
<pre>$config = HTMLPurifier_Config::createDefault();
$config->set('HTML.DefinitionID', 'enduser-customize.html tutorial');
$config->set('HTML.DefinitionRev', 1);
$config->set('Cache.DefinitionImpl', null); // remove this later!
$def = $config->getHTMLDefinition(true);
<strong>$def->addA
|
