$_SERVER['HTTP_REFERER'] missing
<p>I want to use <code>$_SERVER['HTTP_REFERER']</code> in my site but i get the following:</p>

<pre><code>Notice: Undefined index: HTTP_REFERER 
</code></pre>

<p>I have tried printing <code>$_SERVER</code>. This outputs the following:</p>

<pre><code>Array
(
    [HTTP_HOST] =&gt; 192.168.1.10
    [HTTP_USER_AGENT] =&gt; Mozilla/5.0 (X11; Ubuntu; Linux i686; rv:15.0) Gecko/20100101 Firefox/15.0
    [HTTP_ACCEPT] =&gt; text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8
    [HTTP_ACCEPT_LANGUAGE] =&gt; en-us,en;q=0.5
    [HTTP_ACCEPT_ENCODING] =&gt; gzip, deflate
    [HTTP_CONNECTION] =&gt; keep-alive
    [PATH] =&gt; /sbin:/usr/sbin:/bin:/usr/bin
    [SERVER_SIGNATURE] =&gt; Apache/2.2.3 (CentOS) Server at 192.168.1.10 Port 80
    [SERVER_SOFTWARE] =&gt; Apache/2.2.3 (CentOS)
    [SERVER_NAME] =&gt; 192.168.1.10
    [SERVER_ADDR] =&gt; 192.168.1.10
    [SERVER_PORT] =&gt; 80
    [REMOTE_ADDR] =&gt; 192.168.1.77
    [DOCUMENT_ROOT] =&gt; /var/www/html
    [SERVER_ADMIN] =&gt; root@localhost
    [SCRIPT_FILENAME] =&gt; /var/www/html/sandeep/test/hash.php
    [REMOTE_PORT] =&gt; 53851
    [GATEWAY_INTERFACE] =&gt; CGI/1.1
    [SERVER_PROTOCOL] =&gt; HTTP/1.1
    [REQUEST_METHOD] =&gt; GET
    [QUERY_STRING] =&gt; 
    [REQUEST_URI] =&gt; /sandeep/test/hash.php
    [SCRIPT_NAME] =&gt; /sandeep/test/hash.php
    [PHP_SELF] =&gt; /sandeep/test/hash.php
    [REQUEST_TIME] =&gt; 1347365919
)
</code></pre>

<p>Can anyone help me to find <code>HTTP_REFERER</code> or suggest an alternative to <code>HTTP_REFERER</code>?</p>
