PHP shell_exec does not work with ssh

Question

Shell_exec works correctly in PHP, but when using ssh it does not return any output..

<?php
    echo shell_exec("/usr/bin/ssh -i /tmp/key server 'ls'");
?>

The above command works fine in a bash shell and the following displays the proper output in PHP

<?php
    echo shell_exec("ls");
?>

I was hoping this could be done without using a third party php library...

Answer 1

Using phpseclib, a pure PHP SSH2 implementation :

<?php
include('Net/SSH2.php');

$ssh = new Net_SSH2('www.domain.tld');
$key = new Crypt_RSA();
$key->loadKey(file_get_contents('/tmp/key'));
if (!$ssh->login('username', $key)) {
    exit('Login Failed');
}


echo $ssh->exec('ls');
?>