根据选定的itemid更新foreach循环中的Mysql行

I am trying to update some rows in mysql based on selected checkbox,but my query is updating all the rows in the table. Please check below code:

    if (!empty($_POST['checkbox'])) 
    {
    // Loop to store and display values of individual checked checkbox.
        foreach ($_POST['checkbox'] as $selected) {
            $sql1="UPDATE Items SET Status='1' WHERE Item_Id='$selected'";
            $result1=mysql_query($sql1);
            if (!$result1) 
            {
                echo "Error While updating";
            }
            else
            {
               header("Refresh: 2;url=Main_Menu.php");
               mysql_close($conn);
               echo "<p>Todays Menu Updated <a href='Main_Menu.php>Click here</a> if you     are not redirected automatically in 2 seconds<br /></p>";
           } 
       }

Here if (!empty($_POST['checkbox'])) you should use the name of your checkbox.

For instance, if your html is like below:

  <input type="checkbox" name="checkbox_name" />

You should write the if statement as below:

if (!empty($_POST['checkbox_name']))

The same holds for the foreach statement and the use of this in your sql statement.