PHP SSH execute gnome-calculator (ubuntu)

我使用php和ssh，并希望执行图形程序，如gnome-calculator。我该怎么做呢?这是我的代码:

    <?php
   if (!function_exists("ssh2_connect")) die("function ssh2_connect doesn't exist");
// log in at server1.example.com on port 22
if(!($con = ssh2_connect("localhost", 22))){
    echo "fail: unable to establish connection'n";
} else {
    // try to authenticate with username root, password secretpassword
    if(!ssh2_auth_password($con, "terminator", "root")) {
        echo "fail: unable to authenticate'n";
    } else {
        // allright, we're in!
        echo "okay: logged in...'n";
    $get = $_GET['cmd'];
        // execute a command
        if (!($stream = ssh2_exec($con, $get ))) {
            echo "fail: unable to execute command'n";
        } 
    else {
            // collect returning data from command
            stream_set_blocking($stream, true);
            $data = "";
            while($line = fgets($stream)) {
    echo nl2br($line);
}
            fclose($stream);
        }
    }
}
?>
`

我可以执行ls -a或mkdir等命令。但我不能得到像一个应用程序来执行图形界面(如执行gnome计算器)，我该怎么做呢?我这样使用我的代码:http://localhost/index.php?cmd=ls%20-a

只是在胡闹!