Unbeatable Tic-Tac-Toe

Select	Select	O
Select	X	Select
Select	Select	Select

Fatal error: Uncaught Error: Call to a member function getElementsByTagName() on null in /usr/local/www/apache24/data/tictactoe/index.php:38 Stack trace: #0 /usr/local/www/apache24/data/tictactoe/index.php(113): update_element('t7860', 'moves', '__O_X____') #1 /usr/local/www/apache24/data/tictactoe/index.php(334): generate('__O_X____', 't7860') #2 {main} thrown in /usr/local/www/apache24/data/tictactoe/index.php on line 38