Problema com ssh2_connect

Pessoal,

Estou tentando executar o seguinte script PHP:

<?phpclass SFTPConnection{	private $connection;	private $sftp;	public function __construct($host, $port=22)	{ $this->connection = ssh2_connect($host, $port); if (! $this->connection) throw new Exception("Could not connect to $host on port $port.");	}	public function login($username, $password)	{ if (! @ssh2_auth_password($this->connection, $username, $password)) throw new Exception("Could not authenticate with username $username " . "and password $password."); $this->sftp = @ssh2_sftp($this->connection); if (! $this->sftp) throw new Exception("Could not initialize SFTP subsystem.");	}	public function uploadFile($local_file, $remote_file)	{ $sftp = $this->sftp; $stream = @fopen("ssh2.sftp://$sftp$remote_file", 'w'); if (! $stream) throw new Exception("Could not open file: $remote_file"); $data_to_send = @file_get_contents($local_file); if ($data_to_send === false) throw new Exception("Could not open local file: $local_file."); if (@fwrite($stream, $data_to_send) === false) throw new Exception("Could not send data from file: $local_file."); @fclose($stream);	}}try{	$sftp = new SFTPConnection("201.63.164.17", 22);	//$sftp->login("root", "root");	//$sftp->uploadFile("/tmp/to_be_sent", "/tmp/to_be_received");}catch (Exception $e){	echo $e->getMessage() . "\n";}?>

Está dando este erro:

Fatal error: Call to undefined function ssh2_connect() in C:\Arquivos de programas\Apache Software Foundation\Apache2.2\htdocs\moodle\dmdweb\teste.php on line 10

Estou usando PHP 1.5.6 e Apache 2.2.3.

Consigo fazer esse acesso usando o putty.

Vinicius.