<form action="sell.php" method="post">
    <fieldset>
        <div class="form-group">
        Stock:
        <?php
        $rows = query("SELECT symbol FROM portfolio WHERE id = ?", $_SESSION["id"])
        foreach($rows as $row)
        ?>
            <select name = "stock">
                <option> value = <?= $row["symbol"] ?> </option>
            </div>
        <?php endforeach ?>
    </fieldset>
</form>
<div>
    or <a href="register.php">register</a> for an account
</div>