PDO显示多个表列

Question

I'm trying to execute two almost identical queries. But for some reason it keeps loading if I execute them both.

Here is my code:

$query = "show columns from auto_new";
$stmtColumns = $db->prepare($query);
$stmtColumns->execute();
$result = $stmtColumns->fetchAll(PDO::FETCH_BOTH);

foreach($result as $r) {
    $velden .= $r["0"]. "| ";
}

$query = "show columns from auto_coc";
$stmtColumnsCoc = $db->prepare($query);
$stmtColumnsCoc->execute();
$resultCoc = $stmtColumnsCoc->fetchAll(PDO::FETCH_BOTH);

foreach($resultCoc as $r) {
    $velden .= $r["0"]. "| ";
}

If I only execute one of two queries it works just fine, but both doesn't work at all.

Also tried the following with no luck: $auto_new = 'auto_new'; $auto_coc = 'auto_coc';

$query = "SELECT * FROM information_schema.columns
          WHERE TABLE_NAME =:auto_new OR TABLE_NAME = :auto_coc";
$stmt = $db->prepare($query);
$stmt->bindParam(':auto_new', $auto_new, PDO::PARAM_STR);
$stmt->bindParam(':auto_coc', $auto_coc, PDO::PARAM_STR);
$stmt->execute();
$result = $stmt->fetchAll(PDO::FETCH_BOTH);

In both ways it keeps loading forever. What am I doing wrong?