在点击提交按钮上显示div

I have a radio button and a submit button. On click of this submit button, I need to display a div.

My code is as follows:

<form action="" method="GET" name="myform">
    <input type="radio" name="ID" value="total" id="radioInputValue"/>
    <input type="submit" name="details1" value="Details"
           onclick="return showDiv();"/>

    <div id="element_to_pop_up" style="display: none;">
        <?php
        echo "DETAILS";
        if (isset($_GET['details1'])) {
            if (isset($_GET['ID'])) {
                $n = $_GET['ID'];
                echo "VALUE IS = $n";
            }
        } else {
            echo "</br> DETAILS FAILED";
        }?>
    </div>
</form>

My JavaScript:

function showDiv() {
    document.getElementById('element_to_pop_up').style.display = 'block';
    return false;
}

Style:

#element_to_pop_up
{ 
   background-color:#fff;
   border-radius:15px;
   color:#000;
   padding:20px;
   min-width:400px;
   min-height: 180px;
}

I am getting the div on click of the details button. But its not entering the if condition .

Instead its giving the output as:

DETAILS

DETAILS FAILED

I want this as my output:

DETAILS

VALUE IS = total

How can i get this radio button value on clicking submit button, Plz help

just copy paste it: it works fine..

<form action="" method="POST" name="myform">
ONE<input type="radio" name="ID" value="total" id="radioInputValue" />
<input type="submit" name="details1" value="Details" onclick="return showDiv();" />
</form>
<div id="element_to_pop_up">                        
<?php 
echo"DETAILS";
if(isset($_POST['details1']))
{
if(isset($_POST['ID']))
{$n=$_POST['ID'];
echo "VALUE IS = ".$n;
}
else
{
echo"</br> DETAILS FAILED";
}
}
?>
</div>



<script src="//code.jquery.com/jquery-1.11.2.min.js"></script>
<script src="//code.jquery.com/jquery-migrate-1.2.1.min.js"></script>
<script>
function showDiv() {
            document.getElementById('element_to_pop_up').style.display = 'block';
           // return false;
        }
        </script>

Change your submit button like this:

<input type="submit" name="details1" value="Details" onclick="showDiv()" />

When you click your button, it displays the div.

Your PHP code should work, but make sure the file is .php and not .html or .htm.