Weighted Probability - A simple weighted probability system

weights.php

<?php
  // Weight percentage system
  // By: Laffin
  // Gives weights to items, and randomly chooses items based on weight
  
  $items = array(
    array('lint',40),
    array('copper coin',35),
    array('silver coin',15),
    array('gold coin',5),
    array('bank note',5)
  );
  
  // How many loops should we do
  $loops=500;
  
  // Find the total weight of all items
  $total_weight=0;
  foreach($items as $key=>$val)
  {
        $items[$key][2]=$total_weight;
        $total_weight=$items[$key][3]=$val[1]+$total_weight;
        
  }
  
  // initialize our stat counter
  foreach(array_keys($items) as $val)
    $stat[$val]=0;
  for($loop=0;$loop<$loops;$loop++)
  {
      $chance=rand(0,$total_weight);
      // Check Against Item Percent Markers
      $marker=0;
      foreach($items as $key=>$val)
        if($chance<=$val[3]) break;
      // Statistics
      $stat[$key]++;
  }
  
  // Display Found stats for each item
  header('Content-Type: text/plain');
  
  echo "Loop of {$loops}\n";
  echo "Just by weights\n";
  foreach($items as $key=>$val)
  {
      echo "{$val[0]} found {$stat[$key]} times (%". (($stat[$key]/$loop)*100) .") base weight ($val[1]) base percentage(%". number_format((($val[1]/$total_weight)*100),2) .")\n";
  }
?>