Gives the possibility to perform actions according to a certain probability

chance.php

class Chance
{
    private $_aData;

    public function addData($sName, $fPercentage)
    {
        $fPercentage = (float) $fPercentage;

        if ($fPercentage < 1 && $fPercentage > 0) {
            $fPercentage = $fPercentage * 100;
        }
        $this->_aData[] = array(
            'percentage' => $fPercentage,
            'name' => $sName
        );
    }

    public function calculate()
    {
        uasort($this->_aData, function ($a, $b) {
            return $a['percentage'] <=> $b['percentage'];
        });

        $iCounter = 0;
        foreach ($this->_aData as $aData) {
            $iCounter = $iCounter + $aData['percentage'];
        }

        if ($iCounter != 100) {
            return;
        }

        for ($i=0; $i < count($this->_aData); $i++) {
            if ($i == 0) {
                $this->_aData[$i]['min'] = 0;
                $this->_aData[$i]['max'] = $this->_aData[$i]['percentage'];
                continue;
            }

            $this->_aData[$i]['min'] = $this->_aData[$i - 1]['max'];
            $this->_aData[$i]['max'] = $this->_aData[$i - 1]['max'] + $this->_aData[$i]['percentage'];
        }

        $iRand = mt_rand(1, 100);
        foreach ($this->_aData as $aData) {
            if ($iRand > $aData['min'] && $iRand <= $aData['max']) {
                return $aData['name'];
            }
        }
    }
}