PHP "global" variable not accessible in __construct

Question

I have an "game.php" with the following code:

<?php
include("database.php");

class Game {
    var $gameinfo;
    var $gameid;
    var $players;

    function __construct($gameinfo) {
        $this->gameinfo = $gameinfo;
        $this->gameid = $gameinfo["gameid"];

        $this->players = $database->getUserInfosByGameID($this->gameid);
    ...

and an "database.php" with the following code:

<?php

include("constants.php");

class MySQLDB {
    ... constructor etc
    function getUserInfosByGameID($gameid) { }
}
// Create database connection
global $database;
$database  = new MySQLDB();

now when creating a new game-object it throws the error

"variable $database not defined in game.php row 12"

even though in "api.php" it works like this:

<?php
// check for POST method
if($_SERVER["REQUEST_METHOD"] != "POST")
    die();

include("include/database.php");
// get json data
$stream_data = file_get_contents('php://input');
$json = json_decode($stream_data) or die("{valid=false}");

// if session in $json try to get user object from DB
if(isset($json->session))
    $sessionuser = $database->confirmUserSession($json->session);

what am I doing wrong? I've also tried defining $database without global, which also works in "api.php".

You are using include("database.php"); in game.php and include("include/database.php"); in api.php. You sure your paths are correct? — Charlie Fish
– Charlie Fish, Commented Jul 9, 2016 at 17:01
It's because the object MySQLDB is another file. Base on the structure of your code, the object is loaded first before declaring the global variable — Fil
– Fil, Commented Jul 9, 2016 at 17:02
Charlie Fish, yes the path is correct, the game.php and database.php are in subfolder "include" — ThexBasic
– ThexBasic, Commented Jul 11, 2016 at 12:44

Riccardo · Accepted Answer · 2016-07-09 17:22:05Z

2

You should declare global $database in the constructor as well so the method has access to the variable.

function __construct($gameinfo) {
    global $database;
    $this->gameinfo = $gameinfo;
    $this->gameid = $gameinfo["gameid"];

    $this->players = $database->getUserInfosByGameID($this->gameid);

EDIT

Here is the official docs about this topic.

edited Jul 9, 2016 at 17:22

answered Jul 9, 2016 at 17:03

Riccardo

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1 Comment

Riccardo Over a year ago

It works because a class' method is an airtight environment. So it has access only to the class' attributes or the inputs. If you want to use a global variable you have to declare it inside the method so it has visibility of that. You can read the official docs about this topic.

Fil · Accepted Answer · 2016-07-09 17:06:23Z

1

Put your global variable before MySQLDB because class MySQLDB will look for $database.

<?php

global $database;

include("constants.php");

class MySQLDB {
    ... constructor etc
    function getUserInfosByGameID($gameid) { }
}
// Create database connection
$database  = new MySQLDB();

answered Jul 9, 2016 at 17:06

Fil

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