function buildings() {
    global $database;
    global $player;
    global $self_link;


    // Fetch buildings
    $result = $database->query("SELECT * FROM buildings");
    $buildings = array();
    while($building = $database->fetch($result)) {
        $buildings[$building['id']] = $building;
    }

    if(!empty($_POST['build'])) {
        $building_id = (int)$_POST['building_id'];
        $amount = $_POST['amount'];

        try {
            if($player->money < $buildings[$building_id]['cost']) {
                throw new Exception("You do not have enough money to build this!");
            }

            // Purchase technique
            $player->money -= $buildings[$building_id]['cost'] * $amount;
            $database->query("INSERT INTO player_buildings (owner_id, name, power_use, life, att_inf, att_veh, att_air, att_sea)
                                    VALUES ('$_SESSION[user_id]', '$buildings[name]', '$power_use', '$life', '$att_inf', '$att_veh', '$att_air', '$att_sea')");
            $player->update();

            echo "Debugg: Buildings have been added.... I hope..";
        } catch (Exception $e) {
            echo $e->getMessage();
        }

    }
    // Display form
    echo "<table style='width:900px;'>
        <tr>
            <th style='width:40% text-align:left;'>Name</th>
            <th style='width:50%;'>Description</th>
            <th style='width:5%;'>Price</th>
            <th style='width:5%;'>Power Usage</th>
            <th style='width:5%;'>&nbsp;</th>
        </tr>";
        foreach($buildings as $id => $building) {
            echo "<tr>
                <td>{$building['name']}</td>
                <td>{$building['description']}</td>
                <td>{$building['cost']}</td>
                <td>{$building['power_use']}</td>
                <td>
                    <form action='$self_link' method='POST'>
                        <input type='hidden' name='building_id' value='$id' />
                        <input style='width:40px' type='number' name='amount' value='amount' />
                        <input type='submit' name='build' value='Build' />
                    </form>
                </td>
            </tr>";
        }

    echo "</table>";
}

$buildings[$building['id']] = $building;
               ^^^^^^^^^^^^^^^

    VALUES ('$_SESSION[user_id]', '$buildings[name]', '$power_[..snip..]
                                              ^^^^