无法从PHP中的html获取下拉列表值

My first php code gets the values from the table "mytable" which are January, February and March respectively. It works well, I could see Month,January,February and March inside the drop down list. My problem is within the second php code, when I click the search button, nothing happens. What I expected it to do was print out the value from the drop down list but sadly, I get nothing.

<select name="monthchoice">
<option value="">Month</option>; 

<?php   
$request="SELECT date FROM mytable WHERE username='qwe'";
$result=mysqli_query($con, $request);
while($fetch = mysqli_fetch_assoc($result))
{
echo '<option value="'.$fetch['date'].'">'.$fetch['date'].'</option>'; 
}
?>

</select>
<input type="submit" value="Search" name="submit"/>

<?php
if(isset($_POST["submit"]))
{
    if(!empty($_POST['monthchoice']))
        {
        $monthchoice1=$_POST['monthchoice'];
        echo "<br>";
        echo $monthchoice1;
        }
    else
        {
        echo "<br>";
        echo 'Please choose a month!';
        }
}
?>

Have you wrapped your select and input inside a form tag with method post?

<form action="" method="post">
<select name="monthchoice">
<option value="">Month</option>; 

<?php   
$request="SELECT date FROM mytable WHERE username='qwe'";
$result=mysqli_query($con, $request);
while($fetch = mysqli_fetch_assoc($result))
{
echo '<option value="'.$fetch['date'].'">'.$fetch['date'].'</option>'; 
}
?>

</select>
<input type="submit" value="Search" name="submit"/>

<?php
if(isset($_POST["submit"]))
{
    if(!empty($_POST['monthchoice']))
        {
        $monthchoice1=$_POST['monthchoice'];
        echo "<br>";
        echo $monthchoice1;
        }
    else
        {
        echo "<br>";
        echo 'Please choose a month!';
        }
}
?>

</form>

I think you don't use the tag form.