Yet another 'Call to a member function on a non-object' problem - php

Question

I have a html page that calls a php object to get some data back from the database. It works fine, but the script was getting unwieldy so I decided to break some of it out into a bunch of functions.
So I have the following files:
// htdocs/map.php
<?php
include("config.php");
include("rmap.php");
$id = 1;
$gamenumber = getGameNumber($id);
echo $gamenumber;
?>
// htdocs/config.php
<?php
$_PATHS["base"] = dirname(dirname(__FILE__)) . "\\";
$_PATHS["includes"] = $_PATHS["base"] . "includes\\";
ini_set("include_path", "$_PATHS[includes]");
ini_set("display_errors", "1");
error_reporting(E_ALL);
include("prepend.php");
?>
// includes/prepend.php
<?php
include("session.php");
?>
// includes/session.php
<?php
includes("database.php");
class Session {
function Session() {
}
};
$session = new Session;
?>
// includes/database.php
<?php
include("constants.php");
class Database {
var $connection;
function Database() {
$this->connection = mysql_connect(DB_SERVER, DB_USER, DB_PASS) or die(mysql_error());
mysql_select_db(DB_NAME, $this->connection) or die(mysql_error());
}
function query($query) {
return mysql_query($query, $this->connection);
}
};
/* Create database connection */
$database = new Database;
?>
// includes/rmap.php
<?php
function getGameNumber($id) {
$query = "SELECT gamenumber FROM account_data WHERE usernum=$id";
$result = $database->query($query); // line 5
return mysql_result($result, 0);
}
?>
And constants has a bunch of defines in it (DB_USER, etc).
So, map.php includes config.php. That in turn includes prepend.php which includes session.php and that includes database.php. map.php also includes rmap.php which tries to use the database object.
The problem is I get a
Fatal error: Call to a member function on a non-object in
C:\Develop\map\includes\rmap.php on line 5
The usual cause of this is that the $database object isn't created/initialised, but if I add code to show which gets called when (via echo "DB connection created"; and echo "using DB connection";) they are called (or at least displayed) in the correct order.
If I add include("database.php") to rmap.php I get errors about redefining the stuff in constants.php. If I use require_once I get the same errors as before.
What am I doing wrong here?

Answer 1

$database is not in the scope of function GetGameNumber.
The easiest, though not necessarily best, solution is
<?php
function getGameNumber($id) {
global $database; // added this
$query = "SELECT gamenumber FROM account_data WHERE usernum=$id";
$result = $database->query($query); // line 5
return mysql_result($result, 0);
}
?>
global is deemed not perfect because it violates the principles of OOP, and is said to have some impact on performance because a global variable and all its members are added to the function's scope. I don't know how much that really affects performance, though.
If you want to get into the issue, I asked a question on how to organize such things a while back and got some good answers and links.

Answer 2

You need to include
global $database;
at the top of getGameNumber(), since $database is defined outside of getGameNumber itself

Answer 3

Your $database varibleis not accessible from the function's scope automatically. You might need to declare it as global $database; in the function.
Scopes in PHP are explained in the documentation: http://de3.php.net/manual/en/language.variables.scope.php
Please also mind that PHP 4and MySQL3 are out of support for a looooong time and might contain security problems and other unfixed issues.