php game, formula to calculate a level based on exp

Question

Im making a browser based PHP game and in my database for the players it has a record of that players total EXP or experience.

What i need is a formula to translate

Answer 1

The original was based upon a base of 50, thus the 25 scattered across the equation.

This is the answer as a real equation. Just supply your multiplier (base) and your in business.

$_level = floor( floor( ($_multipliter/2)
                      + sqrt( ($_multipliter^2) + ( ($_multipliter*2) * $_score) ) 
                      ) 
                      / $_multipliter
               ) ;