How to use PHP to access MySQL tables and form XML documents

How do I use PHP to access MySQL tables and form XML documents?
Want to make a dynamic tree directory through Php+mysql+dtree+xml, but do not know how to make table material and import XML document through PHP?
Which Warrior has a good way to achieve? It would be nice to have a better way to implement a directory tree, such as a tree structure like csdn.

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The question should not be:

PHP generates XML
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Please give the XML format required by Dtree
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Nagging, your avatar is a thing, I look at the long time is not see what is!!
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Save all the content that needs to be written in the XML file into a string (the "$str. =" "is the best way)
Use the function file_put_contents (' Aaa.xml ', $str).

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Nagging, your avatar is a thing, I look at the long time is not see what is!!

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