Which DB is better than MySQL?

Which DB is better than MySQL?

Last 4 years i have use MySQL for my PHP Project, Recently i did one
Project in PHP with MySQL. Right now the project having more than .7
million records, and yes the website getting slow.
So i am planning to choose any other DB to increase my site performance. I
don't bother about if i can't migrate my existing MySQL data into some DB
which is give more performance than MySQL.
Because its the Application that every year they close the Records, and
they won't need them next Accounting Year.
So please, Help me to find Better DB for my PHP Project, even its not Open
Source.
Thanks in Advance.