Unable to add namespace to an attribute with PHP's SimpleXML

Question

I am creating an Atom feed, when I tried below to add xmlns:i as an attribute -

$node->addAttribute("xmlns:i","http://www.w3.org/2001/XMLSchema-instance"); 

I got this as an output -

i="http://www.w3.org/2001/XMLSchema-instance"

"xmlns:" part was cut off. do I need to escape the :-character? Or is they any other way to add this namespace?

Answer 1

If you want to add an attribute from the namespace/prefix i to $node don't bother declaring the namespace beforehand. Just use the third parameter of addAttribute() to provide the namespace uri for the prefix you're using in the first parameter.

$node = new SimpleXMLElement('<root></root>');
$node->addAttribute("i:somename", "somevalue", 'http://www.w3.org/2001/XMLSchema-instance'); 
echo $node->asXml();

prints

<?xml version="1.0"?>
<root xmlns:i="http://www.w3.org/2001/XMLSchema-instance" i:somename="somevalue"/>

If the attribute itself isn't needed, you can then remove it with unset(), leaving the namespace declaration.

unset($node->attributes('i', TRUE)['somename']);