2048.php

<?php

$game = new Game();

while (true) {
    $game->cycle();
}

class Game
{
    private $field;
    private $fieldSize;
    private $command;
    private $error;
    private $lastIndexX, $lastIndexY;
    private $score;
    private $finishScore;

    function __construct()
    {
        $this->field = array();
        $this->fieldSize = 4;
        $this->finishScore = 2048;
        $this->score = 0;
        $this->addNumber();
        $this->render();
    }

    public function cycle()
    {
        $this->command = strtolower($this->readchar('Use WASD, q exits'));
        $this->cls();

        if ($this->processCommand()) {
            $this->addNumber();
        } else {
            if (count($this->getFreeList()) == 0) {
                $this->error = 'No options left!, You Lose!!';
            } else {
                $this->error = 'Invalid move, try again!';
            }
        }
        $this->render();
    }

    private function readchar($prompt)
    {
        readline_callback_handler_install($prompt, function () {
        });
        $char = stream_get_contents(STDIN, 1);
        readline_callback_handler_remove();
        return $char;
    }

    /**
     * Insert a number in an empty spot on the field
     */
    private function addNumber()
    {
        $freeList = $this->getFreeList();
        if (count($freeList) == 0) {
            return;
        }
        $index = mt_rand(0, count($freeList) - 1);
        $nr = (mt_rand(0, 9) == 0) ? 4 : 2;
        $this->field[$freeList[$index]['x']][$freeList[$index]['y']] = $nr;
        return;
    }

    /**
     * @return array(array('x' => <x>, 'y' => <y>)) with empty positions in the field
     */
    private function getFreeList()
    {
        $freeList = array();
        for ($y = 0; $y < $this->fieldSize; $y++) {
            for ($x = 0; $x < $this->fieldSize; $x++) {
                if (!isset($this->field[$x][$y])) {
                    $freeList[] = array('x' => $x, 'y' => $y);
                } elseif ($this->field[$x][$y] == $this->finishScore) {
                    $this->error = 'You Win!!';
                }
            }
        }
        return $freeList;
    }

    /**
     * Process a command:
     * @return is the command valid (Did it cause a change in the field)
     */
    private function processCommand()
    {
        if (!in_array($this->command, array('w', 'a', 's', 'd', 'q'))) {
            $this->error = 'Invalid Command';
            return false;
        }
        if ($this->command == 'q') {
            echo PHP_EOL . 'Bye!' . PHP_EOL;
            exit;
        }

        // Determine over which axis and in which direction we move:
        $axis = 'x';
        $sDir = 1;

        switch ($this->command) {
            case 'w':
                $axis = 'y';
                $sDir = -1;
                break;
            case 'a':
                $sDir = -1;
                break;
            case 's':
                $axis = 'y';
                break;
            case 'd':
                break;
        }

        $done = 0;
        // shift all numbers in that direction
        $done += $this->shift($axis, $sDir);
        // merge equal numbers in opposite direction
        $done += $this->merge($axis, $sDir * -1);
        // shift merged numbers in that direction
        $done += $this->shift($axis, $sDir);
        return $done > 0;
    }

    private function shift($axis, $dir)
    {
        $totalDone = 0;
        for ($i = 0; $i < $this->fieldSize; $i++) {
            $done = 0;
            foreach ($this->iterate($axis, $dir) as $xy) {
                if ($xy['vDest'] === NULL && $xy['vSrc'] !== NULL) {
                    $this->field[$xy['dX']][$xy['dY']] = $xy['vSrc'];
                    $this->field[$xy['sX']][$xy['sY']] = NULL;
                    $done++;
                }
            }
            $totalDone += $done;
            if ($done == 0) {
                // nothing to shift anymore
                break;
            }
        }
        return $totalDone;
    }

    private function merge($axis, $dir)
    {
        $done = 0;
        foreach ($this->iterate($axis, $dir) as $xy) {
            if ($xy['vDest'] !== NULL && $xy['vDest'] === $xy['vSrc']) {
                $this->field[$xy['sX']][$xy['sY']] += $xy['vDest'];
                $this->field[$xy['dX']][$xy['dY']] = NULL;
                $this->score += $this->field[$xy['sX']][$xy['sY']];
                $done++;
            }
        }
        return $done;
    }

    /**
     * @return array List of src, dest pairs and their values to iterate over.
     */
    private function iterate($axis, $dir)
    {
        $res = array();
        for ($y = 0; $y < $this->fieldSize; $y++) {
            for ($x = 0; $x < $this->fieldSize; $x++) {
                $item = array('sX' => $x, 'sY' => $y, 'dX' => $x, 'dY' => $y, 'vDest' => NULL, 'vSrc' => NULL);

                if ($axis == 'x') {
                    $item['dX'] += $dir;
                } else {
                    $item['dY'] += $dir;
                }

                if ($item['dX'] >= $this->fieldSize || $item['dY'] >= $this->fieldSize || $item['dX'] < 0 || $item['dY'] < 0) {
                    continue;
                }

                $item['vDest'] = (isset($this->field[$item['dX']][$item['dY']])) ? $this->field[$item['dX']][$item['dY']] : NULL;
                $item['vSrc'] = (isset($this->field[$item['sX']][$item['sY']])) ? $this->field[$item['sX']][$item['sY']] : NULL;
                $res[] = $item;
            }
        }
        if ($dir < 0) {
            $res = array_reverse($res);
        }
        return $res;
    }

    /// RENDER ///

    /**
     * Clear terminal screen
     */
    private function cls()
    {
        echo chr(27) . chr(91) . 'H' . chr(27) . chr(91) . 'J';
    }

    private function render()
    {
        echo $this->finishScore . '! Current score: ' . $this->score . PHP_EOL;

        if (!empty($this->error)) {
            echo $this->error . PHP_EOL;
            $this->error = NULL;
        }
        $this->renderField();
    }

    private function renderField()
    {
        $width = 5;
        $this->renderVSeperator($width);
        for ($y = 0; $y < $this->fieldSize; $y++) {
            for ($x = 0; $x < $this->fieldSize; $x++) {
                echo '|';
                if (!isset($this->field[$x][$y])) {
                    echo str_repeat(' ', $width);
                    continue;
                }
                printf('%' . $width . 's', $this->field[$x][$y]);
            }
            echo '|' . PHP_EOL;
            $this->renderVSeperator($width);
        }
    }

    private function renderVSeperator($width)
    {
        echo str_repeat('+' . str_repeat('-', $width), $this->fieldSize) . '+' . PHP_EOL;
    }

}