PHP Update session values after form submit

Question

I have a form with a textbox that requires a date value (date1). When date1 is updated and submitted (posts to same page), it updates the session value with no issues but doesn't update date2 - Explained below.

When date1 is updated date2 doesn't update. Date2 will get a value by adding 30 days to date1.

In summary: Date1 - session variable gets updated after submitting the form. Date2 - session variable does not get updated after submitting the form. BUT both date1 & date2 updates in the database.

I have spent days trying to find the issue. I figured out how to get date1 to update the session variable but date2 I cannot figure it out.

Note: I echo the session variable. That's how I know it's not updating on the page. The echo isn't in the code below.

if(isset($_POST['submit'])){

$memberid = $_SESSION['memberid'];  
$date1 = $_POST['date1'];
$date2 = $_SESSION['date2'];    

if(empty($_POST['date1'])){
$errordate1[] = 'Select a Date';
$_SESSION['date1'];

} else {

echo $_SESSION['date1'] = $_POST['date1'];

}


if(empty($_POST['date2'])){

$_SESSION['date2'];

} else {

echo $_SESSION['date2'] = $_POST['date2'];

}



if(!isset($errordate1)){

$date1 = date('Y-m-d', strtotime($_POST['date1']));
$date2 = date('Y-m-d', strtotime($date1 . " +30 days"));
echo $date2; // I do not get the updated date.  
//die($date2); // if I uncomment this line I get the updated value for date2.


    try {

    $_SESSION['date2'] = $_POST['date2'];
    $stmt = $db->prepare('UPDATE theDates SET date1 = :date1, date2 = :date2, WHERE 
memberid=:memberid');
    $stmt->execute(array(':date1'=>$date1, ':date2'=>$date2, ':memberid'=>$memberid));

    header('Location: profile.php');
    exit;

     } catch(PDOException $e) {
        $errordate1[] = $e->getMessage();
     }

    }

    } 

HTML - I added a hidden value for date2 for testing. Thought I would try it and see what happens to trying to get something to work.

<form method="post" action="prof.php">
<input name="date1" type="text" value="<?php if(isset($errordate1)){ echo $_POST['date1']; } ?>" />
<input name="date2" type="hidden" value="<?php echo $_SESSION['date2']; ?>" />
<input type="submit" name="submit" value="Submit">
</form>

Answer 1

Finally found a way to get this to work rather than relying on a bunch of kids. The whole time during the process of changing the code I used:

$_SESSION['date2'] = $_POST['date2'];

But that was wrong. Instead it's:

$_POST['date2'] = $date2; 

The code:

if(!isset($errordate1)){

    $date1 = date('Y-m-d', strtotime($_POST['date1']));
    $date2 = date('Y-m-d', strtotime($date1 . " +30 days"));

    if(isset($_POST['date2'])) { 
       $_POST['date2'] = $date2; 

       }

    }