<form method="post" action="verify.php">
First Name: <input type="text" name="name1"><br />
Last Name: <input type="text" name="name2"><br />
<input type="submit" name="button" value="Send..">
</form>

<?php
//we verify with the empty() function if the field name1 and name2 are empty
if(empty($_POST['name1']) OR empty($_POST['name2']))
{
//if one of them is empty we print an error message
print 'the field First name and/or Last name is/are empty'; 
}
//else we print a confirmation message 
else{
print 'Thank you '.$_POST['name1'];
}
?>

<?php
//we verify with the regex() function, there are others ways to do this...
//but that will be for the comming lessons.
if(!ereg("\.",$_POST['email']) || !ereg("@",$_POST['email']))
{
//the . or @ or both doesn't exist on the email field
print 'The email address is not valid';
}
else{
print 'email address is ok';
}
?>