Simple Conway's Game of Life

conway.php

<?php
/**
 * Conway's Game of Life
 * @see https://en.wikipedia.org/wiki/Conway's_Game_of_Life
 */

define('SIZE', 36);
define('DISPLAY_ALIVE', '☼');
define('DISPLAY_DEAD', ' ');
define('DISPLAY_NEWLINE', PHP_EOL);
define('SLEEP', 100000);
define('START_TIME', microtime(true));

/**
 * Creates a random scenario of a given size.
 * @param int $size
 * @return array
 */
function createScenario(int $size) : array {
    $scenario = [];

    for ($i = 0; $i < $size; $i++) {
        for ($j = 0; $j < $size; $j++) {
            $scenario[$i][$j] = random_int(0, 1);
        }
    }

    return $scenario;
}

/**
 * Converts an scenario to a string for display
 * @param array $scenario
 * @return string
 */
function render(array $scenario) : string {
    $output = '';
    foreach ($scenario as $row) {
        $output .= join('', array_map(function ($value) {
            return $value ? DISPLAY_ALIVE : DISPLAY_DEAD;
        }, $row));
        $output .= DISPLAY_NEWLINE;
    }

    return $output;
}

/**
 * @param array $scenario
 * @return array
 */
function updateScenario(array $scenario) : array {
    $size = sizeof($scenario);
    $newScenario = $scenario; // Clone scenario.

    for ($i = 0; $i < $size; $i++) {
        for ($j = 0; $j < $size; $j++) {
            $aliveNeighbors = countAliveNeighbors($i, $j, $scenario);
            $initialValue = $scenario[$i][$j];

            // Apply rules...
            if ($initialValue === 0) {
                if ($aliveNeighbors === 3) {
                    $newScenario[$i][$j] = 1;
                } else {
                    $newScenario[$i][$j] = 0;
                }
            }

            if ($initialValue === 1) {
                switch ($aliveNeighbors) {
                    case 0:
                    case 1:
                        // Any live cell with fewer than two live neighbours dies, as if caused by underpopulation.
                        $newScenario[$i][$j] = 0;
                        break;
                    case 2:
                    case 3:
                        // Any live cell with two or three live neighbours lives on to the next generation.
                        $newScenario[$i][$j] = 1;
                        break;
                    case 4:
                    case 5:
                    case 6:
                    case 7:
                    case 8:
                        // Any live cell with more than three live neighbours dies, as if by overpopulation.
                        $newScenario[$i][$j] = 0;
                        break;
                    default:
                        throw new LogicException('The number of alive neighbors is wrong: ' . $aliveNeighbors);
                }
            }
        }
    }

    return $newScenario;
}

/**
 * Counts the number of alive neighbors on an scenario for a given cell.
 * @param int $x
 * @param int $y
 * @param array $scenario
 * @return int
 */
function countAliveNeighbors(int $x, int $y, array $scenario) : int {
    return array_sum([
        (!empty($scenario[$x - 1][$y - 1])) ? $scenario[$x - 1][$y - 1] : 0, // top left
        (!empty($scenario[$x - 1][$y])) ? $scenario[$x - 1][$y] : 0, // top center
        (!empty($scenario[$x - 1][$y + 1])) ? $scenario[$x - 1][$y + 1] : 0, // top right
        (!empty($scenario[$x][$y - 1])) ? $scenario[$x][$y - 1] : 0, // middle left
        (!empty($scenario[$x][$y + 1])) ? $scenario[$x][$y + 1] : 0, // middle right
        (!empty($scenario[$x + 1][$y - 1])) ? $scenario[$x + 1][$y - 1] : 0, // bottom left
        (!empty($scenario[$x + 1][$y])) ? $scenario[$x + 1][$y] : 0, // bottom center
        (!empty($scenario[$x + 1][$y + 1])) ? $scenario[$x + 1][$y + 1] : 0, // bottom right
    ]);
}

/**
 * Returns some useful info (memory usage, elapsed time, population, generation)
 * @param array $scenario
 * @param int $generation
 * @return string
 */
function getScenarioInfo(array $scenario, int $generation) : string {
    $memory = round(memory_get_usage() / 1048576, 2);
    $time = secondsToTimeString(microtime(true) - START_TIME);
    $population = array_reduce($scenario, function(&$res, $item) {
        return $res + array_sum($item);
    }, 0);

    return join(PHP_EOL, [
        sprintf('%.2F MB, %s', $memory, $time),
        sprintf('Size: %d, Population: %d, Generation: %d', sizeof($scenario), $population, $generation),
    ]);
}

/**
 * Formats the elapsed time as a string.
 *
 * @see https://github.com/sebastianbergmann/php-timer/blob/master/src/Timer.php#L55-L74
 * @param float $time
 * @return string
 */
function secondsToTimeString(float $time) : string
{
    $ms = round($time * 1000);
    foreach ([
        'hour'   => 3600000,
        'minute' => 60000,
        'second' => 1000
    ] as $unit => $value) {
        if ($ms >= $value) {
            $time = floor($ms / $value * 100.0) / 100.0;
            return $time . ' ' . ($time == 1 ? $unit : $unit . 's');
        }
    }

    return $ms . ' ms';
}


/**
 * Begin program
 */

system('clear');

$scenario = createScenario(SIZE);
$generation = 1;

do {
    echo join(PHP_EOL, [
        render($scenario),
        getScenarioInfo($scenario, $generation)
    ]);

    $scenario = updateScenario($scenario);
    $generation++;

    usleep(SLEEP);
    system('clear');
} while (true);