Stuck with trying to show tictactoe values out of mysql db - php

Question

I am making a tictactoe game with php and mysql. It should be played by 2 players from different systems. So I have a table in mysql with a column id which goes from 1-9 and a column tictac which has a value X or O or NULL. Put a x or o in the database is working but retrieving a X or O out of the table and show it on the screen is not working. I have a config file, a class.tictactoe.php, class.game.php and an index.php. The DB connection should be in the class.tictactoe.php but I don't know how.
I am having the most trouble with this part:
function displayGame()
{
if (!$this->isOver())
{
echo "<div id=\"board\">";
$i=1;
for ($x = 0; $x < 3; $x++)
{
for ($y = 0; $y < 3; $y++)
{
require('config.inc.php');
$db = new PDO("mysql:dbname=$db_name;host=$db_host",
$db_user, $db_pass,
[PDO::ATTR_ERRMODE => PDO::ERRMODE_EXCEPTION]);
echo "<div id=\"$i\" class=\"board_cell\">";
$i++;
$query = $db->prepare('SELECT * FROM tictactoe WHERE value IS NOT NULL and id = ?');
if ($this->board[$x][$y])
$query->execute([$lookup[$key]]);
echo "<p>\"{$this->board[$x][$y]}\"</p>";
else
{
echo "<select name=\"{$x}_{$y}\">
<option value=\"\"></option>
<option value=\"{$this->player}\">{$this->player}</option>
</select>";
}
echo "</div>";
}
echo "<div class=\"break\"></div>";
}
echo "
<p align=\"center\">
<input type=\"submit\" name=\"move\" value=\"Take Turn\" /><br/>
<b>It's player {$this->player}'s turn.</b></p>
</div>";
}
else
{
if ($this->isOver() != "Tie")
echo successMsg("Congratulations player " . $this->isOver() . ", you've won the game!");
else if ($this->isOver() == "Tie")
echo errorMsg("Whoops! Looks like you've had a tie game. Want to try again?");
session_destroy();
echo "<p align=\"center\"><input type=\"submit\" name=\"newgame\" value=\"New Game\" /></p>";
}
}
function move($postdata)
{
if ($this->isOver())
return;
require('config.inc.php');
$db = new PDO("mysql:dbname=$db_name;host=$db_host",
$db_user, $db_pass,
[PDO::ATTR_ERRMODE => PDO::ERRMODE_EXCEPTION]);
$postdata = array_unique($postdata);
$lookup = ['0_0'=>1, '0_1'=>2, '0_2'=>3, '1_0'=>4, '1_1'=>5, '1_2'=>6,
'2_0'=>7, '2_1'=>8, '2_2'=>9];
$query = $db->prepare('UPDATE tictactoe SET tictac = ? WHERE id = ?');
foreach ($postdata as $key => $value)
{
if ($value!=$this->player) continue;
$query->execute([$this->player, $lookup[$key]]);
if ($value == $this->player)
{
$coords = explode("_", $key);
$this->board[$coords[0]][$coords[1]] = $this->player;
if ($this->player == "X")
$this->player = "O";
else
$this->player = "X";
$this->totalMoves++;
}
}
if ($this->isOver())
return;
}
The indentation might be wrong.