Database class conflicts with other classess

Question

I have been in toruble with kind of conflict issue. There is a Database Class which contains connection, update, delete, insert, fetch methods and also there is User Class which extends Database Class.

class User extends Database {...}

Problem is, when I initialize the Database class and User Class at the same time in "index.php", I get an fatal error which says "Fatal error: Cannot redeclare class Database".

include "database.class.php";
include "user.class.php;
$db = new Database;
$db->connect();

So, I am aware of initializing database class twice, but how can prevent not to happen? P.S.: I can use Database class in other new classes.

`require_once("database.class.php");` instead of `include` wherever you are including it. — Michael Berkowski, Apr 02 '12 at 19:40
possible duplicate of [PHP: cannot redeclare class](http://stackoverflow.com/questions/3769909/php-cannot-redeclare-class) — Michael Berkowski, Apr 02 '12 at 19:41
It doesnt work Michael. There is still same error unfortunately. — Ali Emre Çakmakoğlu, Apr 02 '12 at 19:45
You have to use require_once('database.class.php') instead of include *wherever* you are using it. You can't just replace it in one spot, otherwise the second attempt to include will have this error. — kingcoyote, Apr 02 '12 at 19:48
Thanks all of you. It is normally working..(by using require_once). — Ali Emre Çakmakoğlu, Apr 02 '12 at 19:55

score 1 · Answer 1 · answered Apr 02 '12 at 20:04

Change the two "includes" you have for "require_once", as Michael said:

require_once "database.class.php";
require_once "user.class.php";
$db = new Database;
$db->connect();

Besides, if within the file "user.class.php" you are including the file "database.class.php", change it to "require_once" too.

I hope it helped!

score 1 · Accepted Answer · answered Apr 02 '12 at 20:10

1

In OOP the extends means "is a". What you have written there says: "User is a Database". Which is certifiably bonkers.

Instead of extending the database class, you should be injecting it into constructor of User instance:

$database = new Database(...);
$database->connect();
$user = new User( $database );

Always favor composition over inheritance.

As for all that require_once mess .. just learn how to use spl_autoload_register().

answered Apr 02 '12 at 20:10

tereško

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Can you give an example how am I gonna use? how should constructor of user class supposed to be? This usage is kind of strange to me. – Ali Emre Çakmakoğlu Apr 02 '12 at 20:34
@GncArt , constructor of any class should be only assigning values to local variables. In a well written object oriented code, constructors don't do any "work". – tereško Apr 02 '12 at 20:40
@GncArt , if you really want to learn more about OOP, you should watch few lectures on subject. If you scroll to "OOP beyond classes" part of [this comment](http://stackoverflow.com/questions/9846220/php-oop-core-framework/9855170#9855170), there will be a list of video on the subject. Watch them. You will learn a lot from them .. I sure did. – tereško Apr 03 '12 at 06:26

Database class conflicts with other classess

2 Answers2