matrix multiplier

muliplier.php

<?php

namespace Something;

class MatrixMultiplier
{
    private $matrices;

    public function __construct(array $matrices)
    {
        $this->matrices = $matrices;
    }

    public function multiply(): array
    {
        $matricesLength = count($this->getMatrices());

        if ($matricesLength < 2) {
            throw new \Exception('at least two matrix needs in order to multiply them');
        }

        $result = $this->getNthMatrix(0);

        for ($i = 1; $i < $matricesLength; $i++) {
            $result = $this->multiply2Matrix($result, $this->getNthMatrix($i));
        }

        return $result;
    }

    private function multiply2Matrix(array $leftMatrix, array $rightMatrix)
    {
        $result = [];

        $rightMatrixColumns = count($rightMatrix[0]);

        foreach ($leftMatrix as $index => $rows) {
            for ($j = 0; $j < $rightMatrixColumns; $j++) {
                $result[$index][$j] = $this->dot($rows, array_column($rightMatrix, $j));
            }
        }

        return $result;
    }

    private function dot(array $rows, array $cols): float
    {
        $result = 0;
        foreach ($rows as $index => $row) {
            $result += $row * $cols[$index];
        }
        return $result;
    }

    /**
     * @return array
     */
    public function getMatrices(): array
    {
        return $this->matrices;
    }

    /**
     * @param int $i
     * @return mixed
     */
    private function getNthMatrix(int $i)
    {
        return $this->getMatrices()[$i];
    }
}