Ben onay kutusunu aşağı açılan bir değişiklik istiyorum, ben öncelikle onay kutusunu yoluyla veritabanına saklamak önce seçilebilir dizideki listesini seçmek istiyorum çünkü onu değiştirmek istiyorum, böylece aşağıdaki gibi açılan senaryo oldu

<?php
session_start();
define('DEFAULT_SOURCE','Site_A'); 
define('DEFAULT_VALUE',100);
define('DEFAULT_STC','BGS');
include('class/stockconvert_class.php');
$st = new st_exchange_conv(DEFAULT_SOURCE);
if(isset($_GET['reset'])) {
    unset($_SESSION['selected']);
    header("Location: ".basename($_SERVER['PHP_SELF']));
    exit();
}
?>
<form action="do.php" method="post">
<label for="amount">Amount:</label>
<input type="input" name="amount" id="amount" value="1">
<select name="from">
<?php
$stocks = $st->stocks();
asort($stocks);
foreach($stocks as $key=>$stock)
{
    if((isset($_SESSION['selected']) && strcmp($_SESSION['selected'],$key) == 0) || (!isset($_SESSION['selected']) && strcmp(DEFAULT_STC,$key) == 0))
    {
    ?>
    <option value="<?php echo $key; ?>" selected="selected"><?php echo $stock; ?></option>
    <?php
    }
    else
    {
    ?>
    <option value="<?php echo $key; ?>"><?php echo $stock; ?></option>
    <?php   
    }
}
?>
</select>
<input type="submit" name="submit" value="Convert">
</form>

aşağıdaki gibi ve ben onay kutusunu bunu değiştirildi

<?php
session_start();
define('DEFAULT_SOURCE','Site_A'); 
define('DEFAULT_VALUE',100);
define('DEFAULT_STC','BGS');
include('class/stockconvert_class.php');
$st = new st_exchange_conv(DEFAULT_SOURCE);
if(isset($_GET['reset'])) {
    unset($_SESSION['selected']);
    header("Location: ".basename($_SERVER['PHP_SELF']));
    exit();
}
?>
<form action="do.php" method="post">
<label for="amount">Amount:</label>
<input type="input" name="amount" id="amount" value="1"><input type="submit" name="submit" value="Convert">
<?php
$stocks = $st->stocks();
asort($stocks);
foreach($stocks as $key=>$stock)
{
    if((isset($_SESSION['selected']) && strcmp($_SESSION['selected'],$key) == 0) || (!isset($_SESSION['selected']) && strcmp(DEFAULT_STC,$key) == 0))
    {
    ?>
    <br><input type="checkbox" id="scb1" name="from[]" value="<?php echo $key; ?>" checked="checked"><?php echo $stock; ?>
    <?php
    }
    else
    {
    ?>
    <br><input type="checkbox" id="scb1" name="from[]" value="<?php echo $key; ?>"><?php echo $stock; ?>
    <?php
    }
}
?>
</form>

ama çalışmıyor, ben ilgili diğer kodlarını görüntülemek için ihtiyaç duyuyorum?

Teşekkürler bazı bir yardım ve bunu takdir eğer

UPDATED: ok post the first apparently less obvious, so I will add the problem of error

the error is Fatal error: Call to undefined method st_exchange_conv::convert() in C:\xampp\htdocs\test\do.php on line 21

line 21 olan $st->convert($from,$key,$date);

session_start();
if(isset($_POST['submit']))
{
    include('class/stockconvert_class.php');
    $st = new st_exchange_conv(DEFAULT_SOURCE);
    $from = mysql_real_escape_string(stripslashes($_POST['from']));
    $value = floatval($_POST['amount']);
    $date = date('Y-m-d H:i:s');
    $_SESSION['selected'] = $from;
    $stocks = $st->stocks();
    asort($stocks);

    foreach($stocks as $key=>$stock)
    {
        $st->convert($from,$key,$date);
        $stc_price = $st->price($value);
        $stock = mysql_real_escape_string(stripslashes($stock));
        $count = "SELECT * FROM oc_stock WHERE stock = '$key'";
        $result = mysql_query($count) or die(mysql_error());
        $sql = '';
        if(mysql_num_rows($result) == 1)
        {
            $sql = "UPDATE oc_stock SET stock_title = '$stock', stc_val = '$stc_price', date_updated = '$date' WHERE stock = '$key'";
        }
        else
        {       
        $sql = "INSERT INTO oc_stock(stock_id,stock_title,stock,decimal_place,stc_val,date_updated) VALUES ('','$stock','$key','2',$stc_price,'$date')";
        }   
        $result = mysql_query($sql) or die(mysql_error().'<br />'.$sql);
    }
    header("Location: index.php");
    exit();
}

Why I want to change it from dropdown to checkbox? because with via checkbox list I will be able to choose which ones I checked it was the entrance to the database, then it seem not simple to me, I looking for some help< thanks So much For You mate.