Should objects be created chronologically as class defined? - php

Question

I am having a strange error while creating objects. While I create an objects in chronological orders as classed defined, it is going on good. But when I change the order or object creation, it gives error.
The classes I am using are as follows:
<?php
class dbClass{
private $dbHost, $dbUser, $dbPass, $dbName, $connection;
function __construct(){
require_once("system/configuration.php");
$this->dbHost = $database_host;
$this->dbUser = $database_username;
$this->dbPass = $database_password;
$this->dbName = $database_name;
}
function __destruct(){
if(!$this->connection){
} else{
mysql_close($this->connection);
}
}
function mysqlConnect(){
$this->connection = mysql_connect($this->dbHost, $this->dbUser, $this->dbPass) or die("MySQL connection failed!");
mysql_select_db($this->dbName,$this->connection);
}
function mysqlClose(){
if(!$this->connection){
} else{
mysql_close($this->connection);
}
}
}
class siteInfo{
private $wTitle, $wName, $wUrl;
function __construct(){
require_once("system/configuration.php");
$this->wTitle = $website_title;
$this->wName = $website_name;
$this->wUrl = $website_url;
}
function __destruct(){
}
function showInfo($keyword){
if($keyword=="wTitle"){
return $this->wTitle;
}
if($keyword=="wName"){
return $this->wName;
}
if($keyword=="wUrl"){
return $this->wUrl;
}
}
}
?>
The problem is when I create objects in the following order, it is working perfectly:
include("system/systemClass.php");
$dbConnection = new dbClass();
$dbConnection -> mysqlConnect();
$siteInfo = new siteInfo();
But if I change the order to following
include("system/systemClass.php");
$siteInfo = new siteInfo();
$dbConnection = new dbClass();
$dbConnection -> mysqlConnect();
It gives error!
Warning: mysql_connect() [function.mysql-connect]: Access denied for user '#####'#'localhost' (using password: NO) in /home/#####/public_html/#####/system/systemClass.php on line 19
MySQL connection failed!

Answer 1

Your problem comes from the unconventional use of a configuration file that is read ONCE, but should be used in all classes.
When you instantiate the dbclass first, the configuration is read, probably variables get assigned, and you use these in the constructor.
After that, instantiating siteinfo will not read that file again, which is less harmful, because you only end up with an empty object that does return a lot of null, but does work.
The other way round, you get a siteinfo object with all the info, but a nonworking dbclass.
My advice: Don't use a configuration file that way.
First step: Remove the require_once - you need that file to be read multiple times.
Second step: Don't read the file in the constructor. Add one or more parameters to the constructor function and pass the values you want to be used from the outside.
Info: You can use PHP code files that configure stuff, but you shouldn't define variables in them that get used outside. This will work equally well:
// configuration.php
return array(
'database_host' => "127.0.0.1",
'database_user' => "root",
// ...
);
// using it:
$config = require('configuration.php'); // the variable now has the returned array