class Ftp {
	private $host, $user, $pass, $port;

    function __construct($host, $user, $pass, $port = null) {
		$this->host = $host;
		$this->user = $user;
		$this->pass = $pass;
		$this->port = $port;
    }

	private function connectIfNeeded(){
		if($this->connection){ return; }
		$this->connection = ftp_connect(.........);
	}

	function __destruct(){
		if($this->connection){
			ftp_close($this->connection);
		}
	}
	function getCWD(){
		$this->connectIfNeeded();
		// ...
	}
	function listFiles(){
		$this->connectIfNeeded();
		// ...
	}
	function getFile($file){
		$this->connectIfNeeded();
		// ...
	}
}