Book-page-167

<?php
abstract class Database{
    static public $connection;
    static public function getConnectionCount(){
        echo "<br>Current connection : ". self::$connection ;
    }

    static public function increaseCount(){
        self::$connection++ ;
    }

    abstract public function connect();
}

class MySQL extends Database{
    public function connect(){ //implement connect
        Database::increaseCount(); //access static method
        echo "<br>Connect to MySQL";
    }

    public function save(){
        echo "<br>Save to Database";
    }
}

$mysql = new MySQL();
$mysql->connect();
$mysql->save();

Database::getConnectionCount(); //access static method

?>