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DOM XML: An Alternative to Expat
The Objects Used In DOM
At this point, you are probably wondering what is a DomNode. This is
a good place to start talking about the objects that are included in
the module. There are five objects defined by DOM: DomDocument,
DomNode, DomAttribute, DomDtd, and DomNamespace. We are going to be
focusing primarily on the DomDocument and DomNode objects because they
are the most useful.
The Node object
Here is an overview of what the DomNode object contains.
class DomNode properties: name content type methods: lastchild() children() parent() new_child( $name,$content ) getattr( $name ) setattr( $name,$value ) attributes()
The properties need some elaboration.
- The name property is the actual tag name of the node. A node which refers to the the title tags would have the name of 'title'.
- The content property is usually empty. However, text nodes use this property to hold text.
- The type property is a constant which defines exactly what kind of object the node is. There can be several types of DomNode objects. A list of constants are online at http://www.php.net/manual/ref.domxml.php. For example, a DomNode containing text would have a type of XML_TEXT_NODE.
The methods need to be explained, as well.
-
lastchild()returns the last entry from a node's children. -
parent()returns a node's parent. For instance, the parent of our title node would be 'book'. -
children()returns an array of a node's child nodes. For example, the children of node author would be 'name' and 'birthdate'. -
new_child()takes a name and some content as arguments and adds a new DomNode to its children. -
getattr()and setattr() both deal with attributes. One fetches the value, the other sets it. -
attributes()returns an array of DomAttribute objects.
The DomDocument object
The DomDocument object is also important.
class DomDocument properties: version encoding standalone type methods: root() children() add_root( $node ) dtd() dumpmem()
The properties are pretty self explanatory.
- 'version' refers to the xml version of the document.
- 'encoding' refers to the text encoding.
- 'standalone' is a boolean value determining whether the document is standalone or not.
- The 'type' property has already been explained. A Document object will most likely have the type of XML_DOCUMENT_NODE.
The methods are pretty simple too.
-
root()returns the root node of a document. If we loaded our sample xml file as a DomDocument object, the root node would refer to 'book'. -
children()works just as it did in DomNode. -
add_root()adds a new root node to the xml document. You would use this if you wanted to supplant the 'book' node with another node. -
dtd()returns the xml document's dtd. -
dumpmem()returns a string representation of the xml data.
