mySQL-->php--->xml

hey all,
got a question that i’m having a hard time figuring out.
I have a database set up like so:

name | category |

n1 | c1 |

n2 | c2 |

n3 | c1 |

so now i want to create an xml file using php that will look like so:

<categories>
<category= “c1” />
<category= “c2” />
</categories>

So that it lists all the categories in the database only once.

Anyone know a way to pull this off with php??
Thanks,
Mat