class.ilArrayElementShuffler.php

Go to the documentation of this file.

<?php
/* Copyright (c) 1998-2013 ILIAS open source, Extended GPL, see docs/LICENSE */


class ilArrayElementShuffler
{
        protected $seed;

        public function __construct()
        {
                $this->setSeed($this->buildRandomSeed());
        }
        
        public function getSeed()
        {
                return $this->seed;
        }

        public function setSeed($seed)
        {
                $this->seed = $seed;
        }

        public function buildRandomSeed()
        {
                list($usec, $sec) = explode(' ', microtime());
                return (int)($sec + ($usec * 100000));
        }

        public function buildSeedFromString($string)
        {
                return hexdec(substr(md5($string), 0, 10));
        }

        public function shuffle($array)
        {
                $this->initSeed($this->getSeed());
                $array = $this->shuffleArray($array);
                $this->initSeed($this->buildRandomSeed());
                return $array;
        }

        private function initSeed($seed)
        {
                $seed = (int)$seed; // (mt_)srand seems to not cast to integer itself (string seeds avoid randomizing) !!

                if( $this->isMtRandomizerAvailable() )
                {
                        mt_srand($seed);
                }
                else
                {
                        srand($seed);
                }
        }

        private function shuffleArray($array)
        {
                if( $this->isMtRandomizerAvailable() )
                {
                        return $this->mtShuffle($array);
                }

                shuffle($array);
                return $array;
        }

        private function mtShuffle($orderedArray)
        {
                $shuffledArray = array();
                
                while( count($orderedArray) > 0 )
                {
                        $key = mt_rand(0, (count($orderedArray)-1));
                        $splice = array_splice($orderedArray, $key, 1);
                        $shuffledArray[] = current($splice);
                }
                
                return $shuffledArray;
        }

        private function isMtRandomizerAvailable()
        {
                return function_exists('mt_srand') && function_exists('mt_rand');
        }
}