Notice: Undefined index: HTTP_REFERER - php

Question

Notice: Undefined index: HTTP_REFERER
$http_referer = $_SERVER['HTTP_REFERER']
i used this from tutorial.and it looks okay
also code is calling it from including file
what should i change?
i added print_r($_SERVER); and now page gives me this
Array ([UNIQUE_ID] => UoSxWa56310AAAwUckIAAAAA
[HTTP_HOST] => movafaghha.com
[HTTP_COOKIE] => __utma=210711305.58608218.1372977010.1372977010.1372977010.1; __utmz=210711305.1372977010.1.1.utmcsr=who.is|utmccn=(referral)|utmcmd=referral|utmcct=/whois/movafaghha.com; PHPSESSID=83eb0e2ae7ebe4b6c2eeb071d9f5de71
[HTTP_X_REAL_IP] => 109.109.41.81
[HTTP_X_FORWARDED_HOST] => movafaghha.com
[HTTP_X_FORWARDED_SERVER] => movafaghha.com
[HTTP_X_FORWARDED_FOR] => 109.109.41.81
[HTTP_CONNECTION] => close
[HTTP_CACHE_CONTROL] => max-age=0
[HTTP_ACCEPT] => text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,*/*;q=0.8
[HTTP_USER_AGENT] => Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/31.0.1650.48 Safari/537.36
[HTTP_ACCEPT_LANGUAGE] => en-US,en;q=0.8,fa;q=0.6
[PATH] => /sbin:/usr/sbin:/bin:/usr/bin
[SERVER_SIGNATURE] =>
[SERVER_SOFTWARE] => Apache
[SERVER_NAME] => movafaghha.com
[SERVER_ADDR] => 174.122.223.93
[SERVER_PORT] => 80
[REMOTE_ADDR] => 109.109.41.81
[DOCUMENT_ROOT] => /home/memarest/public_html/movafaghha.com
[SERVER_ADMIN] => webmaster#movafaghha.memarestan.com
[SCRIPT_FILENAME] => /home/memarest/public_html/movafaghha.com/tutorials/login200/register.php
[REMOTE_PORT] => 49737
[GATEWAY_INTERFACE] => CGI/1.1
[SERVER_PROTOCOL] => HTTP/1.0
[REQUEST_METHOD] => GET
[QUERY_STRING] =>
[REQUEST_URI] => /tutorials/login200/register.php
[SCRIPT_NAME] => /tutorials/login200/register.php
[PHP_SELF] => /tutorials/login200/register.php
[REQUEST_TIME_FLOAT] => 1384427865.54
[REQUEST_TIME] => 1384427865
[argv] => Array ( )
[argc] => 0
)
edited the code but still unable to echo all fiedds are required
<?php
ini_set("display_errors", true);
error_reporting(E_ALL);
require 'core.inc.php';
if(!loggedIn()) {
//check mikunim ke tamame field ha dar form vojod darand va set shudan
if(isset($_POST['username'])&&isset($_POST['password'])&&isset($_POST['password_again'])&&isset($_POST['firstname'])&&isset($_POST['surename'])) {
$username = $_POST['username'];
$password = $_POST['password'];
$password_again = $_POST['password_again'];
$firtsname = $_POST['firstname'];
$surename = $_POST['surename'];
//HALA CHECK MIKUNIM KHALI HASTAND YA NA
if(!empty($username)&&!empty($password)&&!empty($password_again)&&!empty($firstname)&&!empty($surename)){
echo 'ok' ;
} else {
echo ' All fields are required';
}
}
?>
<form action="register.php" method="POST">
Username:<br> <input type="text" name="username"><br> <br>
Password:<br> <input type="password" name="password"><br><br>
Password again:<br> <input type="password" name="password_again"><br><br>
Firstname:<br> <input type="text" name="firstname"><br><br>
Surname:<br> <input type="text" name="surename"><br><br>
<input type="submit" value="register">
</form>
<?php
} elseif (loggedIn()) {
echo 'you \'re already logged in';
}
?>
now after adding
"e"
page says "all fields are required"
but even when fill all fields message do not change

Answer 1

HTTP_REFERER is not guaranteed to be sent by the client:
The address of the page (if any) which referred the user agent to the current page. This is set by the user agent. Not all user agents will set this, and some provide the ability to modify HTTP_REFERER as a feature. In short, it cannot really be trusted.
In your case it's clearly not being sent, so really all you can do is
if(isset($_SERVER['HTTP_REFERER'])) {
//do what you need to do here if it's set
}
else
{
//it was not sent, perform your default actions here
}

Answer 2

if (isset($_SERVER['HTTP_REFERER'])) {$THE_REFER=$_SERVER['HTTP_REFERER']}

Answer 3

Undefined index means the array key is not set, do a:
var_dump($_POST); die();
before the line that throws the error and see that you're trying to get an array key that does not exist.

Answer 4

The Correct way to reffer is
$my_referer = isset($_POST['referer']) ? trim($_POST['referer']) : (isset($_SERVER['HTTP_REFERER']) ? base64_encode($_SERVER['HTTP_REFERER']) : false);