irazasyed · January 8, 2016 09:21 · Jan 8, 2016
diff --git a/weight-utility.php b/weight-utility.php
@@ -0,0 +1,23 @@
+<?php
+  /**
+   * 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;
+      }
+    }
+  }