Question

I’m using mysqli prepared statements in an OOP manner. Everything is working as intended, but I can’t seem to find any documentation on how to detect and then throw an exception during a while loop. This how my code stands at the moment and it works perfectly.

$rslt=array();
$data=array();
$stmt->bind_result($rslt['col1'], $rslt['col2'], $rslt['col3'], $rslt['col4']);
while($stmt->fetch()){
    $data[]=$rslt;
}

However it contains no way of throwing an exception. This is how I throw an exception in a similar script which is limited to 1 result (therefore I don’t need to loop through them on this example).

$rslt=array();
$data=array();
$stmt->bind_result($rslt['col1'], $rslt['col2'], $rslt['col3'], $rslt['col4']);
if(!$stmt->fetch()){
   throw new Exception('Failed to fetch results', 1);
}
$data[]=$rslt;

I’m almost trying to do what is in the code below but it throws the following error:-

“Parse error: syntax error, unexpected T_THROW in xxx/xxx/includes/_xxxClass.php on line 95

while($stmt->fetch()){
    $data[]=$rslt or throw new Exception('Failed to fetch results', 1);
}

What I’m looking for is a way to see if there is an error with fetching the results and then throw an exception inside my while loop.

Thanks in advance!

Answer 1

The test you are performing is flawed. mysqli::fetch() returns false on failure, so your while loop will exit as soon as it sees false. If no results are returned, then the loop will not execute and $data will be empty.

What you need to do instead is test if $data is populated after the while loop and then throw your exception if it is empty:-

while($stmt->fetch()){
    $data[]=$rslt;
}
if(empty($data)) throw new Exception('Failed to fetch results', 1);

On reflection, you shouldn’t be throwing an exception just because no results are returned, just return the empty array:-

Exceptions are for handling exceptional circumstances and an empty result set is not exceptional.