mysql_fetch_array fails sometimes

I'm trying to implement the connection to a online payment framework.

One of the files is giving me some trouble, because sometimes the code works, sometimes it doesn't... And I can't understand why...

Here's where the code is failing...

$sql = "select transidmerchant,totalamount from nsiapay where     transidmerchant='".$order_number."'and trxstatus='Verified'";
$result = mysql_query($sql);
**$checkout = mysql_fetch_array($result);**
echo "sql : ".$sql;
$hasil=$checkout['transidmerchant'];
echo "hasil: ".$hasil;
$amount=$checkout['totalamount'];
echo "amount: ".$amount;
    // Custom Field
if开发者_StackOverflow社区 (!$hasil) {
  echo 'Stop1';
} else {
    if ($status=="Success") {}
}

It's just part of the code but I think it's enough for you to try to see the problem... It fails on the bold line, $checkout = mysql_fetch_array($result); The weird thing is that the "echo sql" works, and it shows the right values, but then when I put them on the array, sometimes the variables are passed, sometimes they're not... And so, when getting to if (!$hasil) it fails because the value is empty... but sometimes it works...

Any ideas on what might be happen?

Thans Luis

---

The only way this fail is when query doesn't return anything.

The correct way would be to check if there is something returned:

$sql = "select transidmerchant,totalamount from nsiapay where     transidmerchant='".$order_number."'and trxstatus='Verified'";
$result = mysql_query($sql);
if($checkout = mysql_fetch_array($result)){
    $hasil = $checkout['transidmerchant'];
    echo "hasil: ".$hasil;
    $amount=$checkout['totalamount'];
    echo "amount: ".$amount;
        // Custom Field
    if (!$hasil) {
      echo 'Stop1';
    } else {
        if ($status=="Success") {}
    }
}else{
    echo "Empty query result";
}