Assigning Vars

[LogicalDohnuts]

Basically I'm trying something out. What I'm trying to accomplish here, is that when you enter data into the textbox (which has text assigned to it) which you have edited/added to the previous text and echo it off. It does that perfectly, but I'm wanting it too save and stay as that, until you decide to write again, is there anyway of doing this? I was thinking about sessions? But it seems too steep.

<form method="post" action="test.php" >
<?php $hello = "SOMETEXT"; ?>
<input type="text" name="getme" value="<?php printf($hello); ?>" />
<br>
<?php

    $GetMod = $_POST['getme'];
    
    $hello += $GetMod;
    
    echo $GetMod;
    
?>
<br>
<input type="submit" name="submit" value="submit" />
</form>