Error - Trying to get property 'num_rows' of non-object [duplicate]

问题

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Reference - What does this error mean in PHP? (35 answers)

mysqli_fetch_assoc() expects parameter / Call to a member function bind_param() errors. How to get the actual mysql error and fix it? (1 answer)

Closed last year.

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?

回答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

来源：https://stackoverflow.com/questions/50975752/error-trying-to-get-property-num-rows-of-non-object