PHP PDO check for mysql error

Question

I have this problem that drives me crazy. All i want is just check a query for an error, if so display error, otherwise run the query.

I have the following almost (since it runs the insert query twice) working

[..]

$dbdata = new mySQLAccessData();
$db = new PDO($dbdata->hostname,$dbdata->username,$dbdata->password);
$defaults = new Defaults();

[..]

if(!$db->exec($sql)){
    echo($defaults->throwError('MySql error',implode(":",$db->errorInfo())));
}else{
    $db->exec($sql);
    $defaults->writeLog($table,$db->lastInsertId(),'add');
}

I tried numerous things (amongst others the try(){}catch(){} method) but nothing worked except for the code above. It shows the error the way i want, and only when an error occurs, but runs the exec() twice...

Can someone bail me out?

Answer 1

If you want to see an exception thrown when an error occurs, just set the PDO error-mode (see also: Connections and Connection management ):

$db = new PDO($dbdata->hostname,$dbdata->username,$dbdata->password);
$db->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);

This for example will make your code throw exceptions automatically. Probably exactly what you're looking for.

The actual issue with your code is doing exec twice. You don't need to:

$success = $db->exec($sql);

if (!$success) {
    echo $defaults->throwError('MySql error', implode(":", $db->errorInfo()));
} else {
    # do not exec *again* here.
    $defaults->writeLog($table, $db->lastInsertId(), 'add');
}

Answer 2

Why do you want to execute the query again in the else part? Usually you just try to run the query and if errors happen, react on them.

[..]

$dbdata = new mySQLAccessData();
$db = new PDO($dbdata->hostname,$dbdata->username,$dbdata->password);
$defaults = new Defaults();

[..]

if(!$db->exec($sql)){
    echo($defaults->throwError('MySql error',implode(":",$db->errorInfo())));
}else{
    $defaults->writeLog($table,$db->lastInsertId(),'add');
}

As far as I know, there is no option to "test" a query before actually executing it.