Generating random results by weight in PHP?

Question

I know how to generate a random number in PHP but lets say I want a random number between 1-10 but I want more 3,4,5's then 8,9,10's. How is this possible? I would post what I have tried but honestly, I don't even know where to start.

Answer 1

Based on @Allain's answer/link, I worked up this quick function in PHP. You will have to modify it if you want to use non-integer weighting.

  /**    * getRandomWeightedElement()    * Utility function for getting random values with weighting.    * Pass in an associative array, such as array('A'=>5, 'B'=>45, 'C'=>50)    * An array like this means that "A" has a 5% chance of being selected, "B" 45%, and "C" 50%.    * The return value is the array key, A, B, or C in this case.  Note that the values assigned    * do not have to be percentages.  The values are simply relative to each other.  If one value    * weight was 2, and the other weight of 1, the value with the weight of 2 has about a 66%    * chance of being selected.  Also note that weights should be integers.    *     * @param array $weightedValues    */   function getRandomWeightedElement(array $weightedValues) {     $rand = mt_rand(1, (int) array_sum($weightedValues));      foreach ($weightedValues as $key => $value) {       $rand -= $value;       if ($rand <= 0) {         return $key;       }     }   }