Unbeatable Tic-Tac-Toe

Fatal error: Uncaught ValueError: array_rand(): Argument #1 ($array) cannot be empty in /usr/local/www/apache24/data/tictactoe/index.php:207 Stack trace: #0 /usr/local/www/apache24/data/tictactoe/index.php(207): array_rand(Array) #1 /usr/local/www/apache24/data/tictactoe/index.php(263): vital_move('XX_XOO_OX') #2 /usr/local/www/apache24/data/tictactoe/index.php(250): comp_move('XX_XOO_OX') #3 /usr/local/www/apache24/data/tictactoe/index.php(316): move('XX_XOO_OX', '0') #4 {main} thrown in /usr/local/www/apache24/data/tictactoe/index.php on line 207