Basically this is the situation.

We have 3 servers which are exactly the same. Each of them runs -
MySQL, Apache - PHP, Freeradius. I want to configure these 3 in a
fashion that would provide the highest availability and reliability.

This is what I was suggested by the tech guy who is going to do this.
Let's say the 3 servers are S1, S2 and S3 (Primary, secondary and
tertiary in that order. The freeradius servers will first talk to the
DB in S1, if it cannot connect to S1 then S2 and if S2 is not
available it looks at the DB in S3. In terms of MySQL synchronization
would this work? S1 and S2 are setup as Master-Slave. I.e the changes
in the DB in S1 is instantaneoulsy reflected in the DB in S2. S2 and
S3 are setup as Master Slave. S1 and S2 are set up as Master-Slave and
this synchronization link takes over only when the Master-Slave link
between S2 and S3 is broken or not available.

Is the above setup possible? Are there any possibilities of database
getting corrupted with this setup. What is best way to do this to
achieve the best reliability plan.