Loading CSV into MySQL using OOP PHP
So I would recommend to not extend the CSV parser from the Database class. 
Instead The CSV parser should get the Database per dependency injection through 
the constructor. Also I would not recommend to access gobal vars like $_SERVER 
in a class. Here an example how you could do that:

class CSVParser
{
    protected $file;
    protected $database;

    public function __construct($file, Database $db)
    {
        $this-&gt;file = $file;
        $this-&gt;db = $db;
    }

    public function saveCSVtoDB()
    {
        // @TODO import CSV to DB
    }
}


And you could use the class with:

$file = isset($_SERVER["argv"][1]) ? $_SERVER["argv"][1] : "stock.csv";

$parser = new CSVParser($file, Database::getInstance());
$parser-&gt;saveCSVtoDB();