Easy way to handle different options

[Piranha]

Hello everyone.

I want to randomize what action should be taken. Each option should have a defined percentage of chance to happen. And it should be easy to change the percentages.

Let's say that I have 3 options, I then want to use option 1 30% of the time, option 2 30% of the time and option 3 40% of the time. After a change option 1 will happen 15% of the time, option 2 25% of the time and option 3 60% of the time. Of course, in the live application it is not 3 options, it is 14 options now and will probably be more in the future.

I know it is possible to use if-statements or select-statements more or less like the pseudocode below, but since it is hard to change it is not an ideal solution for me.

// randomize a variable named $percent that may be between 0 and 99
if ($percent < 30) {
   // option 1
} elseif ($percent < 60) {
   // option 2
} else {
   // option 3
}

Can anyone give me a suggestion about how I could solve this problem?

[laserlight]

One idea would be to do something like this:

function selectWeightedOption($option_weights) {
    $uniform_deviate = mt_rand() / mt_getrandmax();
    $sum = 0;
    foreach ($option_weights as $key => $option_weight)
    {
        $sum += $option_weight;
        if ($uniform_deviate <= $sum)
        {
            return $key;
        }
    }
    return false;
}

$option_weights = array(0.3, 0.3, 0.4);
echo selectWeightedOption($option_weights) . '<br />';

$option_weights = array(0.15, 0.25, 0.6);
echo selectWeightedOption($option_weights);

[NogDog]

Another option:

<?php
$pct = mt_rand(1, 100);
switch(true)
{
   case ($pct <= 30):
      echo "option 1";
      break;
   case ($pct <= 60):
      echo "option 2";
      break;
   default:
      echo "option 3";
      break;
}

[Piranha]

Thanks a lot for the help, I managed to solve it using laserlight's solution. Nice to know I can always come here to get help when I can't find a solution by myself 🙂