Biased Random Value From Array With PHP

Sometimes you will want to get a random value form an array in a biased random way, that is, you will want certain values to be returned more than others. Here is a function that will generate a single key from an array, with a greater change of a higher value being retrieved.

function biasedRandom($numbers){


 $total = 0;


 foreach($numbers as $number=>$weight){


  $total += $weight;


  $distribution[$number] = $total;


 };


 $rand = mt_rand(0,$total-1);


 foreach($distribution as $number=>$weights){


  if($rand


 


This function is used in the following way.


 


//set up array


$array = array('one'=>100,


 'two'=>100,


 'three'=>100,


 'four'=>500);


 


// get biased random number


echo biasedRandom($array);


 


The key that is generated the most by the function is four because it has a higher value than the rest and will therefore 'weigh' a lot more.