math helper to sum fractions

Data.php

<?php

class Snowdog_Math_Helper_Data extends Mage_Core_Helper_Abstract
{
    /**
     * Greatest common divisor using Euclid's algorithm
     *
     * @param int $a
     * @param int $b
     * @return int
     */
    public function gcd($a, $b)
    {
        $a = abs($a);
        $b = abs($b);

        if ($a == 0) {
            return $b;
        } elseif ($b == 0) {
            return $a;
        } elseif ($a > $b) {
            return $this->gcd($b, $a % $b);
        } else {
            return $this->gcd($a, $b % $a);
        }
    }

    /**
     * Least common multiple using Euclid's algorithm
     *
     * @param int $a
     * @param int $b
     * @return int
     */
    public function lcm($a, $b)
    {
        $a = abs($a);
        $b = abs($b);

        if ($a > $b) {
            return ($b / $this->gcd($a, $b)) * $a;
        } else {
            return ($a / $this->gcd($a, $b)) * $b;
        }
    }

    /**
     * Calculates the sum of fractions and round up to the ceiling
     *
     * @param array $fractions Array of items with the following format array(1, 2)
     * @return int
     */
    public function sumFractions(array $fractions)
    {
        $lcm = 0;
        foreach ($fractions as $fraction) {
            list(, $denominator) = $fraction;
            if ($lcm === 0) {
                $lcm = $denominator;
            } else {
                $lcm = $this->lcm($lcm, $denominator);
            }
        }

        $nominatorSum = 0;
        foreach ($fractions as $fraction) {
            list($nominator, $denominator) = $fraction;
            $multiplier = $lcm / $denominator;
            $nominatorSum += $nominator * $multiplier;
        }

        return ceil($nominatorSum / $lcm);
    }
}