Cannot select data after update or delete sql statement in php in same action

[CarolHCX]

 

In the same $-POST , i wanted  to perform update and delete. With the updated and deleted database, I need to select the updated data from the database. However, it tells me:  Warning: mysqli_num_rows() expects parameter 1 to be mysqli_result, boolean given in... .I am new to sql in php, is it true that i cannot perform sql in this way? Or is there any suggestion to perform select straight after deleting and updating?

CANCEL BOOK RESERVATION
if(isset($_POST['cancelres']))
{


        $query = "DELETE FROM reserved_books WHERE id='$resid';"; //delete reservation
        $query .="UPDATE reserved_books SET queue = queue - 1 WHERE bookid = '$bookid' AND queue > '$bookqueue';";//update queue number where reservation that queue behind/after/ the current reservation
        $query_run = mysqli_multi_query($connection, $query);

        if($query_run)
        {
          $_SESSION['success'] = "Reservation Cancelled";
        }
        else
        {
          $_SESSION['status'] = " Reservation Not Cancelled";    
        }

        $query= "SELECT title FROM books WHERE id = '$bookid';"; //get book title from db
        $query_run = mysqli_query($connection,$query);
        if(mysqli_num_rows($query_run)>0)
        {
            foreach ($query_run as $row) {
            $title = $row['title'];
            }
        }
        $bookres = "SELECT * FROM reserved_books WHERE bookid = '$bookid' AND queue = 1";
        $bookres_run = mysqli_query($connection,$bookres);
        foreach($bookres_run as $row)
        {
            $res_username = $row['username'];
            $res_id = $row['id'];
        }

        $query= "SELECT option_value FROM settings WHERE option_name = 'email_temp_rescollect'"; //get email template from db
        $query_run = mysqli_query($connection,$query);
        if(mysqli_num_rows($query_run)>0)
        {
            $row = mysqli_fetch_array($query_run);
            $rescollect_template = $row[0];
        }}

 

[Barand]

If he result of a query is boolean (ie false) then the query failed. Check for failures. Easiest way is to put this line before your mysqli connection line

mysqli_report(MYSQLI_REPORT_ERROR|MYSQLI_REPORT_STRICT);

You must like living on the edge. Embedded variables in the query AND multi query. That's not just opening the door to SQL injection, it's demolishing the whole wall.