I have 2 tables:

tblUser:


+------+-----------+
| id | Name |
+------+-----------+

tblItems(this table accepts multiple checkbox value depending on how many user selected):

+------+-----------+---------------+
| id | items | name_id |
+------+-----------+---------------+

`name_id` will get the value of id in `tblUser`.<br />
I use this code to get the value of id of `tblUser` to `name_id`:

PHP Code:
for ($i=0$i<sizeof($checkbox);$i++){
        
$sql2="INSERT INTO tbl_trainings VALUES (NULL, '".$checkbox[$i]."', (SELECT id FROM tbl_info))";
        
$result2=mysql_query($sql2);
     } 

It works fine on the first `INSERT` of data that will look like this in database:

+------+-----------+---------------+
| id | items | name_id |
+------+-----------+---------------+
| 1 | Bucket | 1 |
+------+-----------+---------------+
| 2 | Tree | 1 |
+------+-----------+---------------+
| 3 | House | 1 |
+------+-----------+---------------+

But in the next or second `INSERT` of data will be an error. The error is

**Subquery returns more than 1 row** from the `mysql_error();`

By the way, this is the full codes:

PHP Code:
    if($_POST["Submit"]=="Submit"){
        
$sql1="INSERT INTO tblUser VALUES (NULL, '$fname', '$lname')";
        
$result1=mysql_query($sql1);
        for (
$i=0$i<sizeof($checkbox);$i++){
        
$sql2="INSERT INTO tblItems VALUES (NULL, '".$checkbox[$i]."', (SELECT id FROM tblUser))";
            
$result2=mysql_query($sql2);
        }
    }

    if(
$result2 && result1){
        echo
"<center>";
        echo
"<h1>";
        echo 
"SUCCESSFUL!";
        echo
"</h1>";
        echo
"</center>";
    }
    else {
        echo 
"ERROR"mysql_error();
    } 
And the desired output in the database would be:

+------+-----------+---------------+
| id | items | name_id |
+------+-----------+---------------+
| 1 | Bucket | 1 |
+------+-----------+---------------+
| 2 | Tree | 1 |
+------+-----------+---------------+
| 3 | House | 1 |
+------+-----------+---------------+
| 4 | Tree | 2 |
+------+-----------+---------------+
| 5 | Air plane | 2 |
+------+-----------+---------------+
| 6 | Bucket | 3 |
+------+-----------+---------------+


Any help would be appreciated.
Thanks in advance.