Is MySQL able to cope with very large projects?

[mat green]

Hi

I am PHP and MySQL programmer who has been given the task of creating a database for up to 1.5 million users. The database will be accessed by Schools around the country where teachers and students will upload their work/download work and participate in a discussion forum. The administration section will be used to add and remove accounts. There is also some basic stuff like newsletters and updateable ‘what’s new’ content.

My question is simply this: Is PHP and MySQL up to such a large scale database with uploads and downloads being a regular activity? I have never done anything on this scale before and need to know if the technology I use is up to it before I accept the assignment. I never use other people class’s, I write all my own code, but if this could be a problem here I would like to know. I believe the maximum session variables is about 1000 for MySQL, could this be changed as every user has to log in with their password. Are there any issues I should be aware of for such a large site. I will be using a dedicated server. Any advice would be much appreciated.

Cheers

Mat