Error Checking for PDO Prepared Statements [duplicate] - php

Question

This question already has answers here:
Why does this PDO statement silently fail?
(2 answers)
Closed 5 years ago.
I'm trying to create proper error handling for queries on a MySQL database using PDO prepared statements. I want the program to exit the moment an error in the prepared statement process is detected. Taking advantage of the fact that each step in the PDO prepared statement process returns False on failure, I threw together this repugnant hack:
global $allFields;
global $db;
global $app;
//dynamically append all relevant fields to query using $allFields global
$selectQuery = 'SELECT ' . implode($allFields, ', ') .
' FROM People WHERE ' . $fieldName . ' = :value';
//prepared statement -- returns boolean false if failure running query; run success check
$success = $selectQueryResult = $db->prepare($selectQuery);
checkSuccess($success);
$success = $selectQueryResult->bindParam(':value', $fieldValue, PDO::PARAM_STR);
checkSuccess($success);
$success = $selectQueryResult->execute();
checkSuccess($success);
with checkSuccess() doing the following:
function checkSuccess($success) {
if ($success == false) {
//TODO: custom error page.
echo "Error connecting to database with this query.";
die();
}
}
Two things. First, this is horribly verbose and stupid. There must be a better way. Obviously I could store the booleans in an array or something to take out a line or 2 of code, but still.
Second, is it even necessary to check these values, or should I just check the result after I perform this line of code:
$result = $selectQueryResult->fetch(PDO::FETCH_ASSOC);
I already have code that does this:
if ($result) { //test if query generated results
// do successful shit
}
else {
echo "404";
$app->response()->status(404); //create 404 response header if no results
As much as I try to break the prepared statement process by inserting weird, mismatched, or lengthy queries, my program always makes it to the $result assignment without returning false on any of the functions where I run checkSuccess(). So maybe I don't need to be checking the above logic at all? Keep in mind that I check for a successful database connection earlier in the program.

Answer 1

I preffer setting the error mode to throwing exceptions like this:
$db->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
right after I connect to the database. So every problem will throw an PDOException
So your code would be:
$selectQuery = '
SELECT
' . implode($allFields, ', ') . '
FROM
People
WHERE
' . $fieldName . ' = :value
';
try
{
$selectQueryResult = $db->prepare($selectQuery);
selectQueryResult->bindParam(':value', $fieldValue);
$selectQueryResult->execute();
}
catch(PDOException $e)
{
handle_sql_errors($selectQuery, $e->getMessage());
}
where the function would be:
function handle_sql_errors($query, $error_message)
{
echo '<pre>';
echo $query;
echo '</pre>';
echo $error_message;
die;
}
In fact I am using a general function that also has something like
$debug = debug_backtrace();
echo 'Found in ' . $debug[0]['file'] . ' on line ' . $debug[0]['line'];
to tell me where was the problem if I am running multiple queries

Answer 2

You have to catch PDOException:
try {
//your code/query
} catch (PDOException $e) {
//Do your error handling here
$message = $e->getMessage();
}
PDOException