modify xml using php <form>

[grape]

hii,

I am stuck and need urgent help.
Though am new with php, i don't know how to modify xml using php. Surfed alot but nothing comes my way.
]
Below is the xml code that need to the modifed, insert or delete child node
<parent>
<child>
<title>title1</title>
<model>model1</model>
<location>mod1.jpg</location>
<info></info>
</child>

<child>
<title>title1</title>
<model>model2</model>
<location>mod1.jpg</location>
<info></info>
</child>
<parent>


I would like to create a form where I can add/modify/delete node detain on a button click. Please help me out ...