PHP array of probability with fractions

Question

i have the following array:

public $percentage = array(
   0 => 20.30,
   1=> 19.96,
   2=> 14.15,
   3=> 45.59
);

// it sums in 100%

I need a random function to return the key by the percentage of the value,

for example: the possibility to get 0 is 20.30% and the possibility to get 2 is 14.15%, the first user got 0, the second one got 2.

Please let me know what is the function you suggest me to use.

Answer 1

Convert the percentages to an accumulated probability, then compare it with a random number.

If the random number falls into a category, outputs the result. If not, move onto the next one until one is found. This allows you to output a number based on the percentage probability stated in the array.

$percentage = array(
   0 => 20.30,
   1=> 19.96,
   2=> 14.15,
   3=> 45.59
);
$random = mt_rand(0,10000)/100;
foreach ($percentage as $key => $value) {
    $accumulate += $value;
    if ($random <= $accumulate) {
        echo $key;
        break;
    }
}