Notice: Trying to get property of non-object

Question

I've built a table in which users register ads. Everyone who submits an ad becomes the owner of that ad. So now I try to get all information related to those ads by providing the username who is the owner.

I've build this funciton:

function get_ad_info_by_username($username,$table_name) {

    $ad_info = array();
    $db = new mysqli("localhost", "root", "", "bazar-rooz") or die ('db connection issue!');
    $query = $db->query("SELECT * FROM `$table_name` WHERE `username` = '$username'");
    $db->query("set names 'UTF8'");
    if ($query->num_rows) { // here I get the error ... property of non-object
        while ($row = $query->fetch_object()) {
            $ad_info[] = $row;
        }
    }
    return $ad_info;
}

I've used the same structure in other functions to get different information. They work fine but this one gives error all the time when I try to run the page to show ads information to the end user.

What is the problem. Can you help me? I'm quite new to PHP and MySQLi

faintsignal: it's actually not an error. It's just a notice but the query doesn't return any rows anyway. It says:

Notice: Trying to get property of non-object in C:\\wamp\\www\\site\\functions\\functions.php on line 261 line 261 is the line I've commented inside the code.

Yeah I think there is an issue with the query but I cant find where.

Answer 1

You are using mysqli wrong way. In many wrong ways to be honest.

However, as with raw mysqli it will take too much extra code, I will show you the proper way using PDO. Nevertheless, all the below guidelines are common for the both drivers:

• first of all, connect to your database only once and then use this sole connection all the way.
• then you should never make table name dynamical. write it right in the query
• also, you ought to use placeholders instead of adding variables directly into query
• last but not least - you have to always have error reporting for the queries turned on , which will relieve all the Good Samaritans from the sin of guesswork.

here it goes

$dsn = "mysql:host=localhost;dbname=bazar-rooz;charset=utf8";
$opt = array(
    PDO::ATTR_ERRMODE            => PDO::ERRMODE_EXCEPTION,
    PDO::ATTR_DEFAULT_FETCH_MODE => PDO::FETCH_ASSOC
);
$pdo = new PDO($dsn,'root','', $opt);

function get_ad_info_by_username($username)
{
    global $pdo;
    $stmt = $pdo->prepare("SELECT * FROM table_name WHERE `username` = ?");
    $stmt->execute([$username]);
    return $stmt->fetchAll();
}
$ads = get_ad_info_by_username('joe');

Answer 2

May be the tablename you are passing to function

get_ad_info_by_username($username,$table_name) is either wrong or does not exist in database.

Because of that

$db->query("SELECT * FROM `$table_name` WHERE `username` = '$username'");

returns value FALSE and hence you're getting the error/warning.