从下拉列表插入值但不插入时没有错误

Question

I have a dropdown loop and when I try to select a number from the drop down it echoes out. but when i insert it, it won't execute or won't display in the database rather. but when I change the $_POST value to a static number, it inserts and displays. like $x=$_POST['category']; it doesn't insert, but $x=3; it inserts in the database Here is what I got :

/*The Drop Down*/
 <select name="category">
 <?php 
 $query=mysql_query("SELECT * FROM deliverable_category");
 while($row=mysql_fetch_assoc($query)){ ?>

 <option value="
 <?php echo $row['deliverable_category_id'] ; ?> ">

 <?php echo $row['deliverable']  ;  ?> 

 </option>
 <?php } ?>

 </select>

/*The Query*/

  $name=$_POST['title'];
  $deliverable_desc=$_POST['deliverable_desc'];
  $category_id=$_POST['category'];
  $adviser=$_SESSION['user_id'];
         $con=mysqli_connect("localhost","root","","obeo") ;
                     if(mysqli_connect_errno())
                     {
                         echo "<br/>Error connecting to database!";
                         exit();
                     }else
                     {
                       echo "<br/> ";

         $sqlstmt="insert into deliverable(deliverable_title,deliverable_desc,adviser_id,deliverable_category_id) values(?,?,?,?)";




            $stmt=$con->prepare ($sqlstmt);
            $stmt->bind_param('ssss', $name,$deliverable_desc,$adviser,$category_id);
            $stmt->execute();   

Answer 1

It should be because you have defined the DB field as INT. Try below code :

$x = (int)$POST['category'];

Answer 2

before you write $adviser=$_SESSION['user_id']; you should use session_start();

if not work , manually execute insert query on your database and check error