"Call to a member function fetch_row() on a non-object" in spite of error handling

Question

I want to execute a query but php/mysql throws

Call to a member function fetch_row() on a non-object

even though

if(!$results) 

should filter out empty results. The error message points to

$row = $results->fetch_row();

This is the whole code:

<?php
$query = 'DELETE FROM `products` WHERE `company` ='.$id_nummer;

$results = $link->query($query);
if(!$results)
{
  echo $link->error;
}
else
{
  $row = $results->fetch_row();
  $wanted_result = $row[0];
}
?>

Where is the cause for this?

EDIT: I solved it by replacing

if(!$results)

with

if(!is_object($results))

and it works.

Solution

You are trying to fetch a row from a a query as an object, however the query that you are making is a DELETE which doesn't return values that can be fetch as a row, but a boolean (TRUE or FALSE) that is the result of the query being successful or not. In this case, $result should return the value TRUE or FALSE, that can be used like this for example:

<?php
$query = 'DELETE FROM `products` WHERE `company` ='.$id_nummer;    
$results = $link->query($query);

if(!$results) {
    echo $link->error;
} else {
    echo "Company id:".$in_number." successfully deleted."
}
?>

Comments

[Jacky Rank]

What is the advantage of using a prepared statement over my approach?

[Michael Berkowski]

@JackyRank The advantage is always security, as you don't require sanitization of the input (though you may still benefit from validation) see also stackoverflow.com/questions/732561/…

[Jacky Rank]

Good. See here: stackoverflow.com/questions/14323476/…

[Michael Berkowski]

@JackyRank I'm glad to see you're trying it out. The effort up front may seem large, but you get used to the few extra lines of code and it really pays off in security. (and the first answer there is correct - you ought not quote the placeholders ? not '?'.

[Jacky Rank]

That leads to "Fatal error: Call to a member function bind_param() on a non-object"