For something I have been doing in a php project of late, I needed to weight an array of values and as I go round and select the values remove the value or -1 from the weight depending on how many of the value are left in the weight.
If you have any improvements or suggestions then id very much like to here them 
$starttime = microtime();
$startarray = explode(" ", $starttime);
$starttime = $startarray[1] + $startarray[0];
/**
* weighted_random()
* Pick a random item based on weights.
*
* @param array $values Array of elements to choose from
* @param array $weights An array of weights. Weight must be a positive number.
* @return mixed Selected element.
*/
function weighted_random($values, $weights){
$count = count($values);
$i = 0;
$n = 0;
$num = mt_rand(0, array_sum($weights));
while($i < $count){
$n += $weights[$i];
if($n >= $num){
break;
}
$i++;
}
return $i;
}
function recalc($val,$values,$weight){
//two steps to consider here, -1 from the weight and if the weight is <=0 unset both the value and the weight.
if($weight[$val]-1<=0){
unset($weight[$val]);
unset($values[$val]);
$new_values = array();
$new_weight = array();
foreach($values as $k=>$v){
$new_values[]=$v;
$new_weight[]=$weight[$k];
}
return array($new_values,$new_weight);
}else{
$weight[$val]=$weight[$val]-1;
return array($values,$weight);
}
}
//in the context of what im doing lets get this right.
$values = array(0=>"164-2",1=>"164-1",2=>"2-2");
$weights = array(0=>1,1=>2,2=>1);
//now we wanna select 4 values but edit them as we go round.
$find = 3;
for($i=0;$i<$find;$i++){
$val = weighted_random($values,$weights);
echo $val.' | ';
echo $values[$val].'
';
list($values,$weights) = recalc($val,$values,$weights);
}
echo 'The new weights are ';
print_r($weights);
echo '
';
$endtime = microtime();
$endarray = explode(" ", $endtime);
$endtime = $endarray[1] + $endarray[0];
$totaltime = $endtime - $starttime;
$totaltime = $totaltime;
echo "This page loaded in $totaltime seconds.";
?>
