Question

Is there any possibility to create a configuration file with global variables that are visible inside the class? Something similar to this:

config.php:

$config['host_address'] = 'localhost';
$config['username '] = 'root';
$config['password'] = 'root';
$config['name'] = 'data';

db.php:

include('config.php');
class DB
{
    private $_config = array($config['host_address'], $config['username'], $config['password'], $config['name']);
    ...

Current property:

private $ _config = array();

I don’t want to transmit through the constructor to my Singleton database connector:

DB::getInstance(array('localhost', 'root', 'root', 'data'));

Answer 1

Your problem is that you are trying to use an expression in the class definition here:

class DB
{
    private $_config = array($config['host_address'], ...

That is syntactically incorrect (you can only use constant values for that), and I wouldn’t expect it to locate the intended scope there. What you should do instead is initialize this property in the construtor instead:

class DB
{
    private $_config;

    function __construct() {
        global $config;
        $this->_config = array($config['host_address'], $config['username'], $config['password'], $config['name']);
    }

Or even lazier, just use include('config.php'); in place of the global $config alias. That way your config script will extract $config as local variable within the constructor, which is all you need.