Error - Trying to get property 'num_rows' of non-object

Question

I want to ask why am I getting this error:

Trying to get property 'num_rows' of non-object

with the following code:

$sql = "SELECT * FROM $table_name ORDER BY Author";
$result = $mysqli->query($sql);
if ($result->num_rows > 0) {...

I have used echo $sql to look if the problem lies there, but there is no problem. My SQL looks fine.

I have tried to use Prepared Statements and got other errors too.

The line which gives the error is the one with the if statement.

Any ideas?

Check for [mysqli errors](http://php.net/manual/en/mysqli.error.php) after your query to find out why it failed. I'm guessing there may be something wrong with `$table_name`, or that table doesn't have a column Author. — aynber, Jun 21 '18 at 18:57
A prepared statement wouldn't actually help you here because you can't bind table names. — user3783243, Jun 21 '18 at 18:59
You can try var_dump($result); and check If this is an object. Probably it's a mysql error. Try mysql_error() to see what is it. — Luma Macagnan, Jun 21 '18 at 19:13
@lumadev They'll need http://php.net/manual/en/mysqli.error.php `mysql_` wont work with `mysqli`. — user3783243, Jun 21 '18 at 19:16

score 1 · Answer 1 · edited Jun 21 '18 at 19:16

1

This is a better (non-error checking) pattern to follow IMO:

$sql = "SELECT * FROM $table_name ORDER BY Author";
$result = $mysqli->query($sql);
if (!empty($result)) {

You should also consider using PDO

edited Jun 21 '18 at 19:16

user3783243

answered Jun 21 '18 at 19:04

TrophyGeek

Why is this better? Isn't this just bypassing the problem and the OP will never get results? – user3783243 Jun 21 '18 at 19:05
Yes, non-error-checking. It's better IMO because it handles lots common failure cases in php and is readable. If the call returns `false`, or `null`, or an empty string `''` or and empty array `[]` all can be handled by `empty()` correctly. – TrophyGeek Jun 21 '18 at 22:19

1 Answers1