I developed a php email activation code for activate user's account after registration, what I want is that if the user click the activation link again after first time, the link will be disabled, any one could help, thanks a lot! here is my php code:
$to = $email;
$subject = " Your Registration";
$message = "Welcome to our website!Thanks for completing registration at www.example.com.
You can complete registration by clicking the following link:http://www.example.com/verify.php?$activationKeyIf this is an error, ignore this email and you will be removed from our mailing list.Regards,\ www.example.com Team";
$headers = 'From: noreply@ example.com' . "
" .
'Reply-To: noreply@ example.com' . "
" .
'X-Mailer: PHP/' . phpversion();
mail($to, $subject, $message, $headers);