escape characters added to form data

Hi,
Some characters entered in the text fields of a form get an escape
character. What is the reason? How can I prevent/remove this?

Here is an example:
<form action=hello.php method=post>
<input type=text value=firstname>
</form>

If the user enters:
O'Hara

And I have the following file hello.php:
<? echo $_POST['firstname']; ?>

The output is
O\'Hara
Received on Mon Oct 24 02:10:09 2005