"include" not working in php file cant reference the function - php

Question

I am trying to put a function that I will commonly use in its own file. Then, I want to include that file so I have access to the function (or so I think).
activity.php (this is the function I want to be able to use)
<?php
function activity() {
$inactive = 600;
// check to see if $_SESSION["timeout"] is set
if (isset($_SESSION["timeout"])) {
// calculate the session's "time to live"
$sessionTTL = time() - $_SESSION["timeout"];
if ($sessionTTL > $inactive) {
$_SESSION["loggedIn"] = false;
session_destroy();
echo "session destroyed";
}
}
else {
echo "You need to log in.";
}
}
?>
Here is showuser.php (the file where the error occurs):
<?php
include ('activity.php');
session_start();
// check to see if $_SESSION["timeout"] is set
activity();
$host="localhost"; // Host name
$uname="root"; // Mysql username
$password="xxx"; // Mysql password
$db_name="itit"; // Database name
$tbl_name="users"; // Table name
// Connect to server and select database.
$mysqli = mysqli_connect($host, $uname, $password, $db_name);
if($_SESSION["loggedIn"]) {
$stmt = $mysqli->prepare("SELECT email FROM users WHERE username = ?");
$stmt->bind_param("s", $_SESSION["username"]);
$stmt->execute();
$stmt->bind_result($em);
$stmt->fetch();
}
else {
echo "You are not logged in.";
}
?>
<h2>Username - Email</h2>
<div id="userinfo"><? echo $_SESSION["username"] ?> - <? echo $em ?></div>
<?
$stmt->close();
mysqli_close($mysqli);
?>
The function should check to see if the session has timed out, unless I am doing something wrong with that code...
I get these errors when running the scripts which include the file:
Warning: include(activity.php) [function.include]: failed to open stream: No such file or directory in /Users/Eamon/Sites/templates/showuser.php on line 2
Warning: include() [function.include]: Failed opening '/activity.php' for inclusion (include_path='.:/Applications/XAMPP/xamppfiles/lib/php:/Applications/XAMPP/xamppfiles/lib/php/pear') in /Users/Eamon/Sites/templates/showuser.php on line 2
Warning: session_start() [function.session-start]: Cannot send session cache limiter - headers already sent (output started at /Users/Eamon/Sites/templates/showuser.php:2) in /Users/Eamon/Sites/templates/showuser.php on line 3
Fatal error: Call to undefined function activity() in /Users/Eamon/Sites/templates/showuser.php on line 6
UPDATE
I did this instead
include ('../activity.php');
This got rid of all the errors except for the "Warning: session_start" error.

Answer 1

Looks like a problem with the directory where PHP is looking for the file.
Try changing it to include ('./activity.php');

Answer 2

If activity.php is in /Users/Eamon/Sites/templates/ you can change your include to
include (__DIR__'."/activity.php');
and it should work for you.