PHP ssh

<?php
class NiceSSH {
    // SSH Host
    private $ssh_host = 'myserver.example.com';
    // SSH Port
    private $ssh_port = 22;
    // SSH Server Fingerprint
    private $ssh_server_fp = 'xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx';
    // SSH Username
    private $ssh_auth_user = 'username';
    // SSH Public Key File
    private $ssh_auth_pub = '/home/username/.ssh/id_rsa.pub';
    // SSH Private Key File
    private $ssh_auth_priv = '/home/username/.ssh/id_rsa';
    // SSH Private Key Passphrase (null == no passphrase)
    private $ssh_auth_pass;
    // SSH Connection
    private $connection;

    public function connect() {
        if (!($this->connection = ssh2_connect($this->ssh_host, $this->ssh_port))) {
            throw new Exception('Cannot connect to server');
        }
        $fingerprint = ssh2_fingerprint($this->connection, SSH2_FINGERPRINT_MD5 | SSH2_FINGERPRINT_HEX);
        if (strcmp($this->ssh_server_fp, $fingerprint) !== 0) {
            throw new Exception('Unable to verify server identity!');
        }
        if (!ssh2_auth_pubkey_file($this->connection, $this->ssh_auth_user, $this->ssh_auth_pub, $this->ssh_auth_priv, $this->ssh_auth_pass)) {
            throw new Exception('Autentication rejected by server');
        }
    }
    public function exec($cmd) {
        if (!($stream = ssh2_exec($this->connection, $cmd))) {
            throw new Exception('SSH command failed');
        }
        stream_set_blocking($stream, true);
        $data = "";
        while ($buf = fread($stream, 4096)) {
            $data .= $buf;
        }
        fclose($stream);
        return $data;
    }
    public function disconnect() {
        $this->exec('echo "EXITING" && exit;');
        $this->connection = null;
    }
    public function __destruct() {
        $this->disconnect();
    }
}
?>