Given you have already used MySQL l would suggest that it would be worth staying with MySQL.
At the moment l am using Access 2000 front end with MySQL backend.
quote "Does it work ?" my answer would have to be yes :-D or do you mean something else ?
This week l am hoping to roll out to 50 users, the user group is only 10 users. So far l have had no speed issues, nor do l expect to. The next step is to roll it out to all 150 people in the company connecting over a LAN and WAN. I would expect the database to cope with this number without any problems.
Regarding migration, there are quite a few articles, about migrating from Access to MySQL, and this is a few products that will do it for you. I use Navicat
http://www.navicat.com/, which will import to and from Access, as well as several other file formats. The MySQL site has a couple of programs that will also do the same task, of going from Access to MySQL.
Forgive my lack of knowledge here, l'm only learning PHP, but l think you might be getting ADODB and ADO mixed up. ADODB, is a libary (think thats correct) for PHP which allows linking to databases. Where as with Access you can use ADO (ActiveX Data Objects) to connect to other databases. I use ADO to connect to the MySQL database, using the MySQL OBDC connector (3.51).
Yes you can use DAO to connect MySQL tables using MySQL OBDC.
Another source of information is
http://www.utteraccess.com, there is a forum dealing with just PHP/MySQL. There are quite a few posts, regarding connecting Access databases to MySQL databases. Couple of the threads l posted deal with ADO connections and DSN-less connections.