PDO, wrong update still no exception - php

Question

try {
$query = 'UPDATE keywords SET value = :keyvalue WHERE keyword = :keyname AND document_id = :docId';
$pdo = _openConnection();
$pdo->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
$pdo->beginTransaction();
$pdoStatement = $pdo->prepare($query);
foreach ($keywords as $keyname => $keyval) {
$pdoStatement->bindParam(':docId', $id, PDO::PARAM_STR);
$pdoStatement->bindParam(':keyname', $keyname, PDO::PARAM_STR);
$pdoStatement->bindParam(':keyvalue', $keyval, PDO::PARAM_STR);
$pdoStatement->execute();
}
$res = $pdo->commit();
var_dump('retornando true', $res);
return true;
} catch (PDOException $e) {
$pdo->rollBack();
echo $e->getMessage();
return false;
}
The sentence updates a given row identified by KEYWORDNAME and DOCUMENT_ID.
I am sending a wrong keyword name (non-existent) but existent document id.
Shouldn't it throw an exception for record not found and rollback the operation?
It is always succeeding and returning true (also I see the var_dump)
PS: this is the last portion of the code.

Answer 1

As far as the database (and thus PDO) is concerned - this is not an error. You performed an update statement, and it successfully updated 0 rows.
If you want to handle this as an error, you'd have to do it manually:
$res = $pdo->commit();
if ($pdo->rowCount() == 0) {
# some exception treatment
}

Answer 2

No, you are simply updating 0 rows when the WHERE condition is not matched. Updating, selecting, etc. 0 rows is not an error, these are normal database operations.
Check the rowCount() to see how many rows are updated and handle that accordingly.

Answer 3

A query which doesn't match any records is NOT an error. It's just an empty result set, which is a perfectly valid result.
The only time you'd get an exception from the query is if there was an actual problem with the query itself, the connection to the db, etc... e.g. A syntax error in the DB, connection failure, permission denied on whatever table(s) you're accessing, etc...