PHP PDO MySQL查询打印空白

Question

Going through a PHP MySQL tutorial and switching the PHP out for PDO; at any rate, my query is coming up blank.

$get_cat = $that->dbh->query("SELECT `cat_name`, `cat_desc` FROM `categories`");

            if(isset($get_cat))
            {
        while($row = $get_cat->fetch(PDO::FETCH_ASSOC))
            {
                printf("
                <tr>
                    <td>".$row['cat_name']." : ".$row['cat_desc']."</td>
                </tr>
                ");
            }
            }
            else
                {
                    echo '<tr><td>return is false</td></tr>';
                }    

$That refers to:

include('db.php');
$that = new lib();    

OLD: So, why is my query blank? Before putting the die in it would return Boolean and give in an error in the loop with the die in it just comes up blank. The categories table has data in it and the page is refreshed on submission for new entries. NEW: Fatal error: Call to a member function fetch() on a non-object in C:\wamp\www\forum\create_category.php on line 36

Line 36 is the while loop line.

Answer 1

You need to tell PDO to throw errors.

$dbh->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
$res = $that->dbh->query("SELECT cat_name, cat_desc FROM categories");
while($row = $res->fetch())
{
    echo "<tr><td>$row[cat_name] : $row[cat_desc]</td></tr>
";
}

run your code, read the error message and take appropriate action

Don't forget to add the first line into your db.php file, to make the setting permanent