View file undo.php

<? /* these functions deal specifically with undoing a move */
	function doUndo()
	{
		global $board, $numMoves;

		/* old PHP versions don't have _POST, _GET and _SESSION as auto_globals */
		if (!minimum_version("4.1.0"))
			global $_POST, $_GET, $_SESSION;
		
		/* get the last move from the history */
		/* NOTE: MySQL currently has no support for subqueries */
		$tmpMaxTime = mysql_query("SELECT Max(timeOfMove) FROM history WHERE gameID = ".$_SESSION['gameID']);
		$maxTime = mysql_result($tmpMaxTime,0);
		$moves = mysql_query("SELECT * FROM history WHERE gameID = ".$_SESSION['gameID']." AND timeOfMove = '$maxTime'");

		/* if there actually is a move... */
		if ($lastMove = mysql_fetch_array($moves, MYSQL_ASSOC))
		{
			/* if the last move was played by this player */
			
				/* undo move */
				$fromRow = $lastMove['fromRow'];
				$fromCol = $lastMove['fromCol'];
				$toRow = $lastMove['toRow'];
				$toCol = $lastMove['toCol'];

				$board[$fromRow][$fromCol] = getPieceCode($lastMove['curColor'], $lastMove['curPiece']);
				$board[$toRow][$toCol] = 0;

				/* check for en-passant */
				/* if pawn moves diagonally without replacing a piece, it's en passant */
				if (($lastMove['curPiece'] == "pawn") && ($toCol != $fromCol) && is_null($lastMove['replaced']))
				{
					if ($lastMove['curColor'] == "black")
						$board[$fromRow][$toCol] = getPieceCode("white", "pawn");
					else
						$board[$fromRow][$toCol] = getPieceCode("black", "pawn");
				}
				
				/* check for castling */
				if ((($board[$fromRow][$fromCol] & COLOR_MASK) == KING) && (abs($toCol - $fromCol) == 2))
				{
					/* move rook back as well */
					if (($toCol - $fromCol) == 2)
					{
						$board[$fromRow][7] = $board[$fromRow][5];
						$board[$fromRow][5] = 0;
					}
					else
					{
						$board[$fromRow][0] = $board[$fromRow][3];
						$board[$fromRow][3] = 0;
					}
				}

				/* restore lost piece */
				if (!is_null($lastMove['replaced']))
				{
					if ($lastMove['curColor'] == "black")
						$board[$toRow][$toCol] = getPieceCode("white", $lastMove['replaced']);
					else
						$board[$toRow][$toCol] = getPieceCode("black", $lastMove['replaced']);
				}

				/* remove last move from history */
				$numMoves--;
				mysql_query("DELETE FROM history WHERE gameID = ".$_SESSION['gameID']." AND timeOfMove = '$maxTime'");

			/* else */
				/* output error message */
		}
	}
?>