<?php
/**
* The Probability Class, extends from abstract Object class.
* It generates one or a group of random events based on probability of each.
* @category Resource
* @package Utility
* @author Hall of Famer(finalized version), xyph(initial script)
* @copyright Mysidia Adoptables Script
* @link http://www.mysidiaadoptables.com
* @since 1.3.3
* @todo Not much at this point.
* @final
*
*/
final class Probability extends Object{
/**
* This will hold our possible outcomes along with thier probabilities.
* I store them with the key being the name of teh event, and the value. it's probability to show up. $this->events['name'] = probability
* @access private
* @var Array
*/
private $events = array();
/**
* Constructor of Probability Class, it can generates events list immediately.
* @access public
* @return Void
*/
public function __construct($events = ""){
if($events instanceof ArrayObject) $this->events = $events->getArrayCopy();
}
/**
* This method will add a new event to the array. I didn't include a check to make sure a duplicate exists.
* So as it is, if you call $this->addEvent( 'blue', 20 );
* followed by $this->addEvent( 'blue', 30 );
* 'blue' will now have a value of 30.
* @param String $value
* @param Int $probability
* @access public
* @return Void
*/
public function addEvent($value, $probability) {
$this->events[$value] = $probability;
}
/**
* Simple method to remove an event. I don't think the array_key_exists() check is needed, but it's there.
* @param String $value
* @access public
* @return Void
*/
public function removeEvent($value){
if(array_key_exists($value, $this->events)) unset($this->events[$value]);
}
/**
* The randEvent method to remove an event. This is where one or multiple random events will be generated.
* @param Int $num
* @access public
* @return String|Array
*/
public function randomEvent($num = 1) {
// Generate a reverse list of events, using our class method below to change the individual probabilities into comparable numbers.
$events = array_reverse( $this->buildEvents(), TRUE );
$sum = array_sum($this->events);
// If only 1 result is needed, we want to return a string. Otherwise, we'll build an array.
if($num == 1){
// Generate the random number between 1 and the sum of all probabilities
$rand = mt_rand( 1, $sum );
// Loop through probabilities, greatest to lowest.
foreach($events as $event => $probability){
if($probability <= $rand) return $event;
}
}
else{
// Set up an empty array to hold the values.
$eventList = array();
// Loop through the following code $num times
for($i = 0; $i < $num; $i++){
// Generate our random number INSIDE the loop, so it gets changed every time
$rand = mt_rand(1, $sum);
foreach($events as $event => $probability){
if($probability <= $rand) {
// If so, add a new array entry. Since we don't need to loop through any more events until we generate a new random number, we use break to escape out of the foreach.
$eventList[] = $event;
break;
}
}
}
return $eventList;
}
}
/**
* The buildEvents method, here's where we modify the events array to become more usable.
* We do this on the fly, rather than when we add an event because it makes removing events a much easier process.
* @access private
* @return Array
*/
private function buildEvents() {
// Create a local copy of the events array. We can change this all we want without modifying data that other class methods might still need.
$events = $this->events;
$total = 0;
// Loop through each probability. The &$event will apply any changes made in the loop to the $events array.
foreach($events as &$probability){
$original = $probability;
$probability = $total;
$total += $original;
}
// Return the momdified event array
return $events;
}
}
?>
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