When I use PHP to set the value of a HTML form input element, it works fine provided I don't have any spaces in the data.
Here's the code:
<input type="text" name="username"
<?php echo (isset($_POST['username'])) ? "value = ".$_POST["username"] : "value = \"\""; ?> />
If I enter "Jonathan" as the username, it is repeated back to me as expected. If I enter "Big Ted", however, I only get "Big" repeated back when I submit the form...
Note that the $_POST["Username"] variable is correct. (I.e. when I echo it using PHP, it is set to Big Ted.)