Bowling Game

classBowlingGame.php

class BowlingGame {

    private $rolls = array();
    private $currentRoll = 0;

    public function __construct() {
        for ($i = 0; $i < 21; $i++) {
            $this->rolls[$i] = 0;
        }
    }

    public function roll($pins) {
        $this->rolls[$this->currentRoll++] = $pins;
    }

    /*     R0    R1    R2    R3    R4    R5      R6      R7      R8      R9    
     *    | 0 1 | 2 3 | 4 5 | 6 7 | 8 9 | 10 11 | 12 13 | 14 15 | 16 17 | 18 19 20 
     */

    public function score() {
        $score = 0;
        $rollNumber = 0; // roll number in round - even numbers - first, odd - second
        for ($round = 0; $round < 10; $round++) {
            if ($this->isStrike($rollNumber)) { // strike
                $score += 10 + $this->rolls[$rollNumber + 1] + $this->rolls[$rollNumber + 2];
                $rollNumber++;
            }
            else if ($this->isSpare($rollNumber)) { // spare
                $score += 10 + $this->rolls[$rollNumber + 2];
                $rollNumber += 2;
            }
            else {
                $score += $this->rolls[$rollNumber] + $this->rolls[$rollNumber + 1];
                $rollNumber += 2;
            }
        }
        return $score;
    }

    private function isSpare($rollNumber) {
        if ($this->rolls[$rollNumber] + $this->rolls[$rollNumber + 1] == 10) {
            return TRUE;
        }
        else {
            return FALSE;
        }
    }

    private function isStrike($rollNumber) {
        if ($this->rolls[$rollNumber] == 10) {
            return TRUE;
        }
        else {
            return FALSE;
        }
    }

    public function getRolls() {
        return $this->rolls;
    }
}