isset function doesn't work

gunheadshot

Lately, I've experienced many problems using isset(). For instance, when I want to know if an user has filled a required field in a form

<?php
if(!isset($_POST['usernmae']))
      echo "Please insert your username.<br>";
?>
<HTML>
<HEAD>
<TITLE>Registration</TITLE>
</HEAD>
<BODY>
<form action="registration.php" method="post">
user name : <input type="text" name="username"><br>
<input type="submit">
</BODY>
</HTML>

When I run this page on my host, if I either fill the username field or don't fill it, I will get the same result. The error message "Please insert your username" will be displayed.

Does anybody know what is the problem? What should I do? How can I fix it?

BTW, if I have grammar or spelling mistakes, please let me know. I want to improve my English.

thorpe

You spelt username incorrectly.

if(!isset($_POST['username']))

Also... be aware that isset doesn't check to see if a variable contains a value, just if it exists. So if a user submitted your form without filling in there username $_POST['username'] is still considered as set to isset.

gunheadshot

Then I should change my IF statement to the following in order to determine if the field isn't empty, right?

$username=trim($_POST['username']);
if($username=="")
      echo "USERNAME field is empty";

thorpe

More like...

if (!isset($_POST['username']) || empty($_POST['username'])) {
  echo "username field is empty";

gunheadshot

Alright, thank you very much!

laserlight

You should simplify that to:

if (empty($_POST['username']))
	echo "username field is empty";

But there's a catch: if the user enters '0', the user will be informed that the field is empty since '0' is considered empty.

Generally this isnt a problem for usernames (since only one possible username poses the exception), but if you want to be certain, use:

if (!isset($_POST['username']) || strlen($_POST['username']) == 0)
	echo "username field is empty";