Example of a Singleton Class

ExampleDatabase.php

<?php

class ExampleDatabase {

    static private $instance = null;

    static public function getInstance()
    {
        if (self::$instance === null) {
            self::$instance = new self();
        }

        return self::$instance;
    }

    private $db = null;

    private function __construct() {}

    public function connect($connection_string)
    {
        return $this->db = pg_connect($connection_string);
    }

    public function query($query)
    {
        return pg_query($this->db, $query);
    }
}


/* configuration */
$example_db = ExampleDatabase::getInstance();
$example_db->connect('dbname=testing');

/* usage */
$example_db = ExampleDatabase::getInstance();
$result = $example_db->query('SELECT * FROM users');