1) php is server side, it could be used to upload an audio file and handle the file server side but you'll need a java applet or a client side program to record the voice message and send it to the server.
2) php could output a link on the page and using html most media formats can be setup for playback. you could use php to pull the audio file from the mysql database but i'd recommend storing the path to the file in the mysql database and placing the file somewhere else on the system.
