How make chance drop items?

Hi!
I have questions, because I write plugin on the drop items with stone, but I dont know how make %.

My config:

Code:

drops:
  items:
    diamond:
      chance: 3.5

You can help me?
I want make %..

can you also put the plugin's PHP up too? ( just so we can see that too? )

I want % drop items with stone.
Example

Code:

if(getChance(3.5))
{
//drop diamond.
}

How create %?

https://en.wikipedia.org/wiki/Percentage
Why can't you simply divide 3.5 by 100?

In java http://pastebin.com/pmdmYnLY
but how make it in php pocketmine?

404
https://en.wikipedia.org/wiki/Percentage

mt_rand(min, max) returns a pseudo-random integer between min and max inclusively.

That means, if you do mt_rand(1, 100), it has a chance to be 1, 2, 3, ..., 99 or 100. Then the chance of it being less than or equal to 0 (<= 0) is 0%. It has 1% chance to be 1, so mt_rand(1, 100) <= 1 has 1% chance to be true. If you check it against 2, it has 2% chance to be true since both outputs of 1 and 2 match the condition. mt_rand(1, 100) <= 99 has 99% chance to be true, because it has 99 numbers that are valid and 1 number that is not valid, hence 99/(99+1) = 99%. mt_rand(1, 100) <= 100 is obviously always true, hence 100%.

Now you understand how to do it?

Yes thanks