Need Some Help With Member Experience Formula

[ShoeLace1291]

I am developing a PHP application that will have a member login and profile system.  I have created a table for storing member's experience(exp) for certain actions.  For example, if they create a new forum thread, add a comment to an article, etc, they will earn a certain amount of exp.  I have found a formula that will calculate the member's exp level.  I need to find their progress percentage based on the exp required for the next level.  For example, if they are level 1 with 75 exp and it takes 100 exp to level up to 2, then they are 75% of the way to level 2. 

 

What this formula I need should do is find out the total exp needed for the next level.  I can get the percentage from there.  Below is the formula I currently am using.  Any help is greatly appreciated!

 

 

 
$experience = 18714;
$level = pow(($experience / 1000), ( 7 / 10));
$level = floor($level);
 
echo $experience; // Would output '7'
 

 

PS:  Any input on adjusting the $level formula to make it harder or easier to level up is welcome!

[requinix]

L = (E / 1000) ^ (7 / 10)
L ^ (10 / 7) = ((E / 1000) ^ (7 / 10)) ^ (10 / 7)
             = (E / 1000) ^ (7 / 10 * 10 / 7)
             = E / 1000
1000 * L ^ (10 / 7) = E

Protip: WolframAlpha is pretty cool

- Solve for E

- Graph of L for E=0 to 20k (shows that you gain levels more slowly)

- Graph of E for L=0 to 50 (shows that it takes more and more experience to level)

- Graph of ΔE for L=0 to 10 (shows how much more experience is required between levels)

 

Comments:

- That's a lot more experience than the 75 and 100 you used in your example. Maybe you want to tone it down?

- This assumes members begin at E=0 L=0. If they start at E=0 L=1 then the equations need to change a little

Edited August 30, 2013 by requinix