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[2008-04-05 21:55 UTC] ezyang@php.net
Description:
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libxml2 is fairly lenient when it comes to what it allows to go into its nodes; you can set attributes and tags with illegal characters in them and it won't complain. The burden is on the userland code to perform an appropriate check with the xmlValidate*() functions.
PHP's DOM implementation is extremely spotty when it comes to these checks, which allows for some broken XML to easily be generated. For example,
$d = new DOMDocument();
$d->appendChild($n = $d->createElement('a'));
$n->setAttribute('"@', 'foo');
echo $d->saveXML();
outputs:
<?xml version="1.0"?>
<a "@="foo"/>
Which is clearly incorrect. However, if I attempt to
$d->createElement('a@');
DOM complains, because xmlValidateName was called on the element name.
Now, I actually don't mind the lack of checking; the DOM tree is useful for things like HTML, where the rules are slightly different from XMLs; an HTML tree can contain a "a@" node, although it would not be valid HTML. (You can try it out for yourself on Firefox by putting that in a document and then inspecting the DOM).
However, I want consistency, and I also want the ability to switch on strict checking when I so desire (especially when I'm producing XML). So I want all-or-nothing production checks in PHP DOM, adding another property in DOMDocument (or maybe even a global libxml configuration option) that specifies whether or not strict production checking should be done.
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Last updated: Mon Apr 21 21:01:26 2025 UTC |
IIRC, DOM does not make any demands on names or things like that. libxml2, which is known for its strictness, doesn't either. So, I'm still hoping that you'll let the checks be turned off. :-) Some things from my investigation: - Double hyphens (--) are not allowed in comments - Most of the text inputs don't check for UTF-8 well-formedness. Haven't tested numeric character entities either, but those are suspicious - Fake namespace declarations in attributes ($d->appendChild($d->createElement('foo:bar')); results in invalid XML, as foo namespace was never defined) All these result in a $d->saveXML(); that is invalid XML, and probably some more.