Fatal error: Uncaught exception 'PDOException' with message 'SQLSTATE[42S21]: Column already exists: 1060 Duplicate column name '0'' in...

$InsertFoo = $pdo->prepare("

    INSERT INTO `MyTbl` (
                            `ColA`,
                            `ColB`
                            )
    SELECT * FROM ( SELECT :a, :b ) AS tmp
    WHERE NOT EXISTS (
        SELECT `MyTbl`.`ColA`
        FROM `MyTbl`
            WHERE `ColA` = :aa
            AND `ColB` = :bb
        )
    LIMIT 1

");

foreach ($loopme as $foo) {

    // query to be executed for ticket insertion
    $TicketsToInsert->execute(array(
                                    a => $foo->fooA,
                                    b => $foo->fooB,
                                    aa => $foo->fooA,
                                    bb => $foo->fooB
                                    ));

}

ALTER TABLE MyTbl ADD UNIQUE (ColA, ColB);

$stmt = $pdo->prepare('INSERT INTO MyTbl (ColA, ColB) VALUES (?, ?)');
foreach ($loopme as $foo) {
    try {
        $stmt->execute([$foo->fooA, $foo->fooB]);
    } catch (PDOException $e) {
        $errorCode = $stmt->errorInfo()[1];
        if ($errorCode == 1586) {
            // I think 1586 is the unique constraint violation error.
            // Trial and error will confirm :)
        } else {
            throw $e;
        }
    }
}