Error when trying to get the button id using PHP

I am generating a list of buttons with the id being a value extracted from a database. Then I want to take this id and display. But, when I try to do that, I get an error. Can some one tell me what I’m doing wrong here.

Button generation

 //This function will display items  
 function showItems($sqlString)
 {
    $result = mysqli_query($this->connectToDb(), $sqlString);
    //var_dump($result);
    if(mysqli_num_rows($result) > 0)
    {           
        foreach ($result as $row) 
        {                 
            echo "<div class='div_item'>";
            echo  "<img src='../images/uploads/".$row['It_image']."' style='width:200px;height:150px;'>"."<br>";
            echo  "IT CODE: ".$row['It_code']."<br>"; 
            echo  "ITEM: ".$row['It_name']."<br>"; 
            echo  "DESC: ".$row['It_desc']."<br>"; 
            echo  "QTY AVAIL: ".$row['qty']."<br>"; 
            echo  "PRICE: ".$row['price']."<br>";
                echo "<form enctype='multipart/form-data' action='' method='POST'>";
                echo  "<button type='submit' name='id' id='".$row['It_code']."'>Buy</button>";
                echo  "</form>";
            echo  "</div>";
        }
   }
}

Displaying the ID when the respective button is clicked

  //get id of the button
  if (isset($_POST['id']))
  {
    echo $_GET['id'];
  }

Error