PHP code included in HTML won't update - php

Question

I currently have a PHP file which will search my MySQL database and see if a user is logged in. If they are logged in, it will echo "Welcome 'username'. Logout" and if they're not logged in it will echo "Login. Register."
If I view this PHP file directly, it will echo out the correct text, depending on whether or not I am logged in. However, if I put into my HTML file using include it will only echo out the logged out text, regardless of whether I'm logged in.
Is there some conflict between PHP and HTML which will stop it from printing out the correct text maybe? It seems strange that it will work opening the PHP file itself, but not when it's included in HTML.
HTML code:
<?php include "loginreg/check.php"; ?>
Would the fact it's in a subfolder make a difference? Haven't included the PHP code as that itself is working, but I have got it if you need to see it.
Cheers
PHP code:
// Gets IP address
$ip = visitorIP();
// Connect to database
mysql_connect(localhost, $username, $password);
#mysql_select_db($database) or die('Unable to select database');
$query = "SELECT * FROM loggedin WHERE userip='$ip'";
$result = mysql_num_rows(mysql_query($query));
if ($result == '0') {
mysql_close();
loggedOut();
return;
}
if (isset($_COOKIE['sid'])) {
$sessionid = $_COOKIE['sid'];
}
$result = mysql_query($query);
while ($row = mysql_fetch_assoc($result)) {
if ($row['sessionid'] == $sessionid) {
mysql_close();
loggedIn($row['id']);
} else {
mysql_close();
loggedOut();
}
}
function visitorIP() {
if (isset($_SERVER['HTTP_X_FORWARDED_FOR'])) {
$TheIp = $_SERVER['HTTP_X_FORWARDED_FOR'];
} else {
$TheIp = $_SERVER['REMOTE_ADDR'];
}
return trim($TheIp);
}
function loggedIn($id) {
global $username, $password, $database;
mysql_connect(localhost, $username, $password);
#mysql_select_db($database) or die('Unable to select database');
$query = "SELECT * FROM users WHERE id='$id'";
$result = mysql_query($query);
while ($row = mysql_fetch_assoc($result)) {
$fname = $row['fname'];
$sname = $row['sname'];
}
echo "<div class=\"fltrt\">Welcome, " . $fname . ". Logout</div>";
}
function loggedOut() {
echo "<div class=\"fltrt\">Login Register</div>";
}

Answer 1

Without seeing the code of both scripts this is just a guess, but a likely problem would be that you are outputting html (anything...) before you include your loginreg/check.php script.
That would render any session_start() statements in your included file useless as the headers already have been sent. And not being able to get to the session would lead to the error that you describe.
Edit: For cookies the same principle applies, they need to be set before the headers are sent so before you output anything to the browser.

Answer 2

Your issue is that you are setting cookies while inside a subdirectory. Use the path parameter of setcookie to ensure you're setting the cookie in the root folder of your website:
// Sets the cookie for the root of the domain:
setcookie("username", "foo", time() + 60 * 60, "/");

Answer 3

Correct me if I'm wrong here, but are you trying to use a PHP include in an HTML file? If so, that will never work (unless you've got some custom server config that will parse PHP code in HTML files).
PHP code is for PHP files. HTML code can work in HTML and PHP files. You cannot do a PHP include, in an HTML file.