Im focusing on a PHP Application the must have numerous of records, what DB must i use, and therefore are there guides on the internet that describes building efficient dbs and tables?
Get acquainted with database normalization. It is a brilliant theory that may help you build stable and scalable databases. There's a great article about them at http://en.wikipedia.org/wiki/Database_normalization
In regards to what database management system you need to use, I'd suggest that starting with MySQL. It is the world's most widely used database software (it's the things they use within WordPress, phpBB and Drupal). It's fast, reliable, free and you will find lots of learning materials about this.
This can be a large subject, basically choosing technology A or B isn't enough. You need to think about the whole chain in the consumer completely up to the net server.
Most DB's are close performance smart. How good you utilise each DB may have an immediate and larger impact than one platform over another.
A badly designed DB schema and poorly optimized query will work badly in almost any db platform.
Don't choose every row (*) just choose the thing you need inside a query.
Always close connections.
Use either prepared claims or escape put user information when placing or upgrading.
MySql is simple to use, but most likely not the best b/c it's free.
SQLite is effective too if you want an embedded database inside your application.