First thing you need to do is the communication with php/mysql application based on JSON or XML (whoever suites you). You have to have a page like website.com/employee_list.php which returns you the XML or JSON that you call from ActionScript.
Then you need a fair knowledge of ActionScript (which isn't a very hard language if you programmed before in C or C-based languages), but don't be scared, the help covers it all.
After that you will require an IDE of choice between Flash or Flex (the second is easier to the beginners due to its large object and display library which helps you create rather fast a good looking application.
The search for employees gives you 2 options to realize it:
- search made via php/mysql and you
just output the results
- search
made via ActionScript searching on
the array of results obtained in 1st
step by requesting to the php/mysql
app the complete list of emplyees
The final step is just to write the code and export the project as an AIR application.
Hope that helps! :)