risb | Running is Beautiful | Data Visualization library

When using namespaces in an XML document, you need to think about three things:

• The namespace URI. This is the globally unique identifier that tools will recognise as being the same namespace (the URI doesn't have to point anywhere, it's just a way of organising who "owns" the identifier).
• The local prefix. This is an arbitrary string which a particular document, or even part of a document, associates with a particular namespace URI, basically just to keep things more compact. This is the part before the : in a tag like . There is also a default namespace for each part of a document, for elements with no prefix.
• The element or attribute name within that namespace. This is the part after the : in a tag like .

I mention all this to understand why the sample XML you provide is invalid, because it looks like you want to use four namespaces:

1. Namespace http://www.xbrl.org/2003/linkbase which you have given the local prefix link
2. An unknown namespace which you have given the local prefix xbrli; I'll call this one http://example.org/xbrli
3. An unknown namespace which you have given the local prefix se-cd-base; I'll call this one http://example.org/se-cd-base
4. An unknown namespace which you have given the local prefix xlink; I'll call this one http://example.org/xlink (unless this was a typo and should have been another reference to http://www.xbrl.org/2003/linkbase?)

Now let's try to construct a valid version of your XML using SimpleXML...

First, we need to create the root element, which is in the http://example.org/xbrli namespace; SimpleXML doesn't have a way to create a document without any nodes, so we have to write the first node by hand and parse it: