<form method="POST" action="<?php echo $_SERVER['SCRIPT_NAME']; ?>" onsubmit="document.getElementById('submit-button').disabled=true;">
I use that line to disable the button after the first click, but it doesnt work..
Here is the line of the button:
<input type="submit" value="Register" id="submit-button"/>
If you are posting to the same page and wish for the button to be disabled after the form has been submitted once, what you can do is use PHP to check if the data that was submitted by the form has been posted to the page. If it has, disable the button. It might look like this:
<form method="POST" action="<?php echo $_SERVER['SCRIPT_NAME']; ?>" <? if (isset($_POST['your_form_data'])) echo "disabled='disabled'" ?> >