It is not possible to use SimpleXML to add a child element without a
namespace prefix to a parent element that has a namespace element. Instead, the
child element inherits the namespace prefix of the parent. So this XML
fragment:
<ns1:parent>
<child>abc</child>
</ns1:parent>
is impossible to construct with SimpleXML. The SimpleXML extension would add
the <child> element with the ns1 namespace prefix. This is a problem for me, as
I have an XML schema that specifies that the child elements must not namespace
qualified.
I looked into the SimpleXML code, and I believe this is actually a bug, as
the code goes through some effort to distinguish between a set but blank
namespace, and a set but not blank namespace. I believe the design intent was
that specifying a blank namespace, would mean that no namespace would be used,
rather than inheriting the namespace of the parent.
<?php
header('Content-Type: text/plain');
$r = new SimpleXMLElement('<r />');
$c1 = $r->addChild('ns1:child1', NULL, 'urn:myspace1');
$c1->addChild('child2');
echo $r->asXML(), "\n";
$r = new SimpleXMLElement('<r />');
$r->addChild('Thing1', 100, '');
echo $r->asXML(), "\n";
Expected result:
----------------
<?xml version="1.0"?>
<r><ns1:child1 xmlns:ns1="urn:myspace1"><ns1:child2/></ns1:child1></r>
<?xml version="1.0"?>
<r><Thing1>100</Thing1></r>
Actual result:
--------------
<?xml version="1.0"?>
<r><ns1:child1 xmlns:ns1="urn:myspace1"><ns1:child2/></ns1:child1></r>
<?xml version="1.0"?>
<r><Thing1 xmlns="">100</Thing1></r>
The current behavior of specifying a blank namespace, is to add a literal
blank namespace (xmlns=""), which isn't a useful result. No one would be
depending on using a blank namepspace to get xmlns="".
The patch is pretty simple:
--- simplexml.c.orig 2011-04-26 16:00:31.000000000 -0700
+++ simplexml.c 2011-04-26 16:00:41.000000000 -0700
@@ -1619,12 +1619,14 @@
localname = xmlStrdup((xmlChar *)qname);
}
+ /* Add new child with no namespace */
newnode = xmlNewChild(node, NULL, localname, (xmlChar *)value);
if (nsuri != NULL) {
+ /* If namespace is not NULL but blank, use no namespace
+ Use this to prevent inheriting the name space of the parent */
if (nsuri_len == 0) {
newnode->ns = NULL;
- nsptr = xmlNewNs(newnode, (xmlChar *)nsuri, prefix);
} else {
nsptr = xmlSearchNsByHref(node->doc, node, (xmlChar *)nsuri);
if (nsptr == NULL) {
(see also http://bugs.php.net/bug.php?id=54354)
If this patch is accepted, I'll also submit patches to clarify the
documentation and add some tests. SimpleXML with the above patch, passes the
existing tests. It is hard to know for sure what the design intent was, as the
code has few comments, few tests, and the documentation is pretty thin. But I
believe the above is correct.
Tom
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