custom xml parser

I am looking to create my own xml based scripting language for a program I am writing. I know that all of the xml parsing tools are with PHP, but I'm not exactly sure how I would implement everything? Can anyone offer any advice, or has an open source scripting language parser for php already been written?? For those that want to know, the reason I'm not just using PHP, is that the product I'm creating needs to be so easy to use that no real programming experience is needed. Scripting is optional, but used when necessary to create custom actions. Take this for example: <setvar> <name>test</name> <value>Hello World!</value> </setvar> <print> <var> <name>test</name> </var> </print> <!-- Prints Hello World! --> or <setvar name="test" value="Hello World!"/> <print> <var name="test"/> </print> <!-- Prints Hello World! --> Both scripts would do the same thing - and it's pretty human-friendly scripting. Can anyone offer advice how to make this work?? Thanks! OHB