weight calculator

PriorityCalculator.php

<?php

/**
 * From a list of items with priorities gets one based on their priority.
 */
 
class PriorityCalculator
{
    public var $data = array();
    public var $universe = 0;

    public function add($data, $probability) {
    	
        $this->data[$x = sizeof($this->data)] = new stdClass;
        $this->data[$x]->value = $data;
        $this->universe += $this->data[$x]->probability = abs($probability);
        
    }

    public function get() {
    	
        if(!$this->universe) {
            return null;
        }
		
        $x = round(mt_rand(0, $this->universe));
        $max = 0;
        $i = 0;

        while($x > $max) {
            $max += $this->data[$i++]->probability;
        }
        
        $val = -1;
        
        if( $this->universe == 1 ) {
            $val = $this->data[$i]->value;
        } else {
            $val = $this->data[$i-1]->value;
        }
		
        return $val;
    }
}