PHP how do i write a multi dimmensional array into file

$board = array(
         array(0,0,0,0,0,0,0,0,0),
         array(0,0,0,0,0,0,0,0,0),
         array(0,0,0,0,0,0,0,0,0),
         array(0,0,0,0,0,0,0,0,0),
         array(0,0,0,0,0,0,0,0,0),
         array(0,0,0,0,0,0,0,0,0),
         array(0,0,0,0,0,0,0,0,0),
         array(0,0,0,0,0,0,0,0,0),
         array(0,0,0,0,0,0,0,0,0)
   );

$row = 0;
    print "<form>";
    print "<table border = 1>";
    while ($row < 8){ // Counts to 8. (from 0...7 = 8 times. 0 ... 8 = 9 times)
       print "<tr>";
       $row++;
       $col = 0; // reset column to 0 each time printing one row.

       while ($col < 8){
        print "<td>";
        if($Board[$row][$col] == 0)
        {
            $value=$row.$col;
            print "<input type="checkbox" name="box[]" value="$value">";
            // Add  before " otherwise it will treat as the end of the quote.

        }
        print "</td>";
        $col++;

       }

       print "</tr>";

    }
    print "</table>";
    print "</form>";

file_put_contents($f, serialize($board));

$board = unserialize(file_get_contents($f));

#dump:
file_put_contents('file_name', serialize($board));
#restore:
$board=unserialize(file_get_contents('file_name'));

#dump:
file_put_contents('file_name', json_encode($board));
#restore:
$board=json_decode(file_get_contents('file_name'));