rendered paste body<? if ((isset($_POST['submit'])==true) && (isset($_POST['checkbox'])==true)) { header("location: http://www.fullurl.com/nextpage.php"); } else if ((isset($_POST['submit'])==true) && (isset($_POST['checkbox'])==false)) { $Error = "You must check the box to continue."; } ?> <html> <head> <body> <form action="test1.php" method="post"> <? if (isset($Error)==true) { echo $Error; } ?> <input type="checkbox" name="checkbox"> You must check this. <input type="submit" name="submit"> </form> </body></html>