Parse error: syntax error, unexpected end of file, expecting ')' in ./Playground/file0.php on line 87

Question

How to solve this problem

Answer 1

You're most likely missing a )

For us to better help you, can you please read the following and update your question:

https://code.sololearn.com/Wek0V1MyIR2r/?ref=app
https://code.sololearn.com/W3uiji9X28C1/?ref=app

Answer 2

This is the last line of your code:
for ($i = 0; $i < $board_size;

I think you are missing a part of your code after this line.