PDO error: SQLSTATE[HY000]: General error: 2031

This same error 2031 can be issued when one bind two values with the same parameter name, like in:

• $sth->bindValue(':colour', 'blue');
• $sth->bindValue(':colour', 'red');

..so, beware.

You cannot use ->bind* and ->execute($params). Use either or; if you pass parameters to execute(), those will make PDO forget the parameters already bound via ->bind*.

This exception also appears if you try to run a query with placeholders instead of preparing a statment such as

$stmt = $db->query('SELECT * FROM tbl WHERE ID > ?');

instead of

$stmt = $db->prepare('SELECT * FROM tbl WHERE ID > ?');