PHP: Database Connection Class Constructor Method

Question

I\'m new to OOP. Originally I was defining variables and assigning values to them within the class and outside of the constructor, but after an OOP lesson in Java today, I was t

Answer 1

The latter is probably better, but with an adjustment: pass some arguments to the constructor, namely the connection info.

Your first example is only useful if you've got one database connection and only if you're happy hard-coding the connection values (you shouldn't be). The second example, if you add say, a $name parameter as an argument, could be used to connect to multiple databases:

I'm new to OOP. Originally I was defining variables and assigning values to them within the class and outside of the constructor, but after an OOP lesson in Java today, I was told this is bad style and should be avoided.

class DatabaseConnection {
    private $dbHost;
    private $dbUser;
    private $dbPass;
    private $dbName;

    function __construct($config) {
        // Process the config file and dump the variables into $config
        $this->dbHost = $config['host'];
        $this->dbName = $config['name'];
        $this->dbUser = $config['user'];
        $this->dbPass = $config['pass'];

        $connection = mysql_connect($this->dbHost, $this->dbUser, $this->dbPass)
            or die("Could not connect to the database:
" . mysql_error());
        mysql_select_db($this->dbName, $connection) 
            or die("Database error:
" . mysql_error());
    }
}

So using this style, you now have a more useful class.