PHP error: mysqli_num_rows () expects parameter 1 to be mysqli_result, boolean given

Question

Possible duplicate:
mysql_fetch_array () expects parameter 1 to be a resource, boolean is set to select

Following is the following error. Line 53 if(mysqli_num_rows($r) == 1) { . How can I fix this problem.

 PHP error: on line 53: mysqli_num_rows() expects parameter 1 to be mysqli_result, boolean given 

Here is the PHP MySQL code.

 $d = "UPDATE users SET del = 1, del_date = NOW() WHERE userid = '" . $_SESSION['userid'] . "'"; $r = mysqli_query ($mysqli, $d) or trigger_error("Query: $d\n<br />MySQL Error: " . mysqli_error($mysqli)); if(mysqli_num_rows($r) == 1) { 

Answer 1

mysqli_query returns a boolean for UPDATE queries. See http://php.net/manual/en/mysqli.query.php . You probably want something like this:

 if (mysqli_affected_rows() == 1) { // ... } 

Answer 2

Since mysqli_query () returns TRUE (1) on UPDATE. mysqli_num_rows () expects some rows to be removed from SELECT, SHOW, DESCRIBE, or EXPLAIN queries.

So:

 if ($r) { 

or use mysqli_affected_rows ()