I'm more knowledgeable of Flex than Flash, but I can give you some pointers.
You'll probably want to have the PHP script output the news items as XML. Some format like:
Code:
<?xml version="1.0" encoding="iso-8859-1"?>
<news>
<item>
<headline>Stix Nix Hick Pix</headline>
<image>http://upload.wikimedia.org/wikipedia/commons/thumb/e/ee/Lange-MigrantMother.jpg/300px-Lange-MigrantMother.jpg</image>
<caption>Migrant Mother</caption>
</item>
...
</news>
When your widget gets the XML document, it fills in the news ticker with items based on the elements in the XML doc.
With Flex, you can bind an HTTPService as the dataProvider for your widget, call "send" on the HTTPService and voila, you've got the data. I'm not as familiar with straight Flash, and I think it does it a little differently. I believe you use an XML object and call its load method (load in Flash CS3), passing in an HTTP URI. The load is asynchronous, so you'll have to add an "onLoad" handler to handle the response. Kirupa.com has an introduction to XML in Flash you might want to check out.
The part I'm least certain about is creating the news item and ticker. That's where Flash and Flex differ the most.