<?php
session_start();
// Check if a new game should be started
if (isset($_POST['new_game'])) {
$_SESSION['board'] = [
['', '', ''],
['', '', ''],
['', '', ''],
];
$_SESSION['currentPlayer'] = PLAYER_X;
$_SESSION['gameOver'] = false;
$_SESSION['gameMessage'] = '';
}
// Initialize the game board if it's not set
if (!isset($_SESSION['board'])) {
$_SESSION['board'] = [
['', '', ''],
['', '', ''],
['', '', ''],
];
$_SESSION['currentPlayer'] = PLAYER_X;
$_SESSION['gameOver'] = false;
$_SESSION['gameMessage'] = '';
}
// Define the player symbols
define('PLAYER_X', 'X');
define('PLAYER_O', 'O');
// Function to check if the game is over
function isGameOver($board) {
return checkWinner(PLAYER_X, $board) || checkWinner(PLAYER_O, $board) || checkTie($board);
}
// Function to check for a win
function checkWinner($player, $board) {
for ($i = 0; $i < 3; $i++) {
if (
($board[$i][0] === $player && $board[$i][1] === $player && $board[$i][2] === $player) ||
($board[0][$i] === $player && $board[1][$i] === $player && $board[2][$i] === $player)
) {
return true;
}
}
if (
($board[0][0] === $player && $board[1][1] === $player && $board[2][2] === $player) ||
($board[0][2] === $player && $board[1][1] === $player && $board[2][0] === $player)
) {
return true;
}
return false;
}
// Function to check for a tie
function checkTie($board) {
foreach ($board as $row) {
if (in_array('', $row)) {
return false;
}
}
return true;
}
// Function to make the AI (player O) move
function makeAIMove($board) {
$bestMove = minimax($board, PLAYER_O)['move'];
$board[$bestMove['x']][$bestMove['y']] = PLAYER_O;
return $board;
}
// Minimax algorithm with Alpha-Beta pruning
function minimax($board, $player, $depth = 0, $alpha = -PHP_INT_MAX, $beta = PHP_INT_MAX) {
$availableMoves = [];
for ($i = 0; $i < 3; $i++) {
for ($j = 0; $j < 3; $j++) {
if ($board[$i][$j] === '') {
$move = ['x' => $i, 'y' => $j];
$board[$i][$j] = $player;
$score = ($player === PLAYER_O) ? -1 : 1;
if (isGameOver($board)) {
if (checkWinner(PLAYER_O, $board)) {
$score = 1;
} elseif (checkWinner(PLAYER_X, $board)) {
$score = -1;
} else {
$score = 0; // It's a tie
}
} else {
$nextPlayer = ($player === PLAYER_O) ? PLAYER_X : PLAYER_O;
$result = minimax($board, $nextPlayer, $depth + 1, $alpha, $beta);
$score = $result['score'];
}
$board[$i][$j] = '';
$move['score'] = $score;
if ($player === PLAYER_O) {
if ($score > $alpha) {
$alpha = $score;
}
} else {
if ($score < $beta) {
$beta = $score;
}
}
if ($alpha >= $beta) {
break 2;
}
$availableMoves[] = $move;
}
}
}
if ($player === PLAYER_O) {
$bestScore = -PHP_INT_MAX;
foreach ($availableMoves as $move) {
if ($move['score'] > $bestScore) {
$bestScore = $move['score'];
$bestMove = $move;
}
}
} else {
$bestScore = PHP_INT_MAX;
foreach ($availableMoves as $move) {
if ($move['score'] < $bestScore) {
$bestScore = $move['score'];
$bestMove = $move;
}
}
}
return ['move' => $bestMove, 'score' => $bestScore];
}
// Handle player moves
if (isset($_POST['x'], $_POST['y']) && !$_SESSION['gameOver']) {
$x = intval($_POST['x']);
$y = intval($_POST['y']);
if ($_SESSION['board'][$x][$y] === '' && $x >= 0 && $x < 3 && $y >= 0 && $y < 3) {
$_SESSION['board'][$x][$y] = $_SESSION['currentPlayer'];
if (checkWinner($_SESSION['currentPlayer'], $_SESSION['board'])) {
$_SESSION['gameMessage'] = 'Player ' . $_SESSION['currentPlayer'] . ' wins!';
$_SESSION['gameOver'] = true;
} elseif (checkTie($_SESSION['board'])) {
$_SESSION['gameMessage'] = "It's a tie!";
$_SESSION['gameOver'] = true;
} else {
// Switch to the other player
$_SESSION['currentPlayer'] = ($_SESSION['currentPlayer'] === PLAYER_X) ? PLAYER_O : PLAYER_X;
// Make AI move
$_SESSION['board'] = makeAIMove($_SESSION['board']);
if (checkWinner(PLAYER_O, $_SESSION['board'])) {
$_SESSION['gameMessage'] = 'Player O wins!';
$_SESSION['gameOver'] = true;
} elseif (checkTie($_SESSION['board'])) {
$_SESSION['gameMessage'] = "It's a tie!";
$_SESSION['gameOver'] = true;
}
}
}
}
?>
<!DOCTYPE html>
<html>
<head>
<title>Tic-Tac-Toe</title>
<style>
table {
border-collapse: collapse;
}
td {
width: 50px;
height: 50px;
text-align: center;
font-size: 24px;
border: 1px solid #000;
}
button {
width: 100%;
height: 100%;
border: none;
background-color: transparent;
font-size: 24px;
cursor: pointer;
}
</style>
</head>
<body>
<h1>Tic-Tac-Toe</h1>
<?php if (!$_SESSION['gameOver']) : ?>
<table>
<?php for ($i = 0; $i < 3; $i++) : ?>
<tr>
<?php for ($j = 0; $j < 3; $j++) : ?>
<td>
<form method="POST">
<input type="hidden" name="x" value="<?php echo $i; ?>">
<input type="hidden" name="y" value="<?php echo $j; ?>">
<button type="submit" <?php echo ($_SESSION['board'][$i][$j] !== '') ? 'disabled' : ''; ?>>
<?php echo $_SESSION['board'][$i][$j]; ?>
</button>
</form>
</td>
<?php endfor; ?>
</tr>
<?php endfor; ?>
</table>
<?php endif; ?>
<p><?php echo $_SESSION['gameMessage']; ?></p>
<form method="POST">
<button type="submit" name="new_game">Start New Game</button>
</form>
</body>
</html>
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