MathPHP\Algebra::extendedGCD PHP Method

    public static function extendedGCD(int $a, int $b) : array
    {
        // Base cases
        if ($a == 0) {
            return [$b, 0, 1];
        }
        if ($b == 0) {
            return [$a, 1, 0];
        }
        $x₂ = 1;
        $x₁ = 0;
        $y₂ = 0;
        $y₁ = 1;
        while ($b > 0) {
            $q = intdiv($a, $b);
            $r = $a % $b;
            $x = $x₂ - $q * $x₁;
            $y = $y₂ - $q * $y₁;
            $x₂ = $x₁;
            $x₁ = $x;
            $y₂ = $y₁;
            $y₁ = $y;
            $a = $b;
            $b = $r;
        }
        return [$a, $x₂, $y₂];
    }