Description:
------------
When I execute command on remote server with 'ssh2_exec' function and executed command is valid, I receive expected result. For example if I execute command 'dir', I receive stream with all directory entries.

But if I execute an invalid command, for example 'dirr', I receive empty stream. When I execute same command using my SSH client (I use PuTTY), I receive the following message: '-bash: dirr: command not found'

I also tried to use callback functions but without success.



Reproduce code:
---------------
$Hostname = 'myhost';
$Username = 'myuser';
$Password = 'mypass';
$Output = null;
$Methods = array();
$Callbacks = array ('ignore'=>'cbIgnore', 'debug'=>'cbDebug', 'macerror'=>'cbMACError', 'disconnect'=>'cbDisconnect');

//connecting remote server...
if (false === $Connection = ssh2_connect($Hostname, 22, $Methods, $Callbacks)) {
  die ("Unable to connect '$Hostname'.\n");
} else {
  echo "Done.\n";
}
//authenticating user...
if (false === ssh2_auth_password($Connection, $Username, $Password)) {
  die ("Unable to authenticate user.\n");
}
//executing command on remote server
if (false === $Stream = ssh2_exec($Connection, 'di')) {
  die ("Unable to execute command on remote server.\n");
}
//set blocking mode on a stream
stream_set_blocking($Stream, true);

//set output string
while ($Block = fread($Stream, 8192)) {
  $Output.= $Block;
}
fclose ($Stream);
echo $Output;

// CALLBACK FUNCTIONS
function cbIgnore ($message)
{
  die ("IGNORE: $message");
}
  
function cbDebug ($message, $language, $always_display)
{
  die ("DEBUG: $message");
}
  
function cbMACError ($packet)
{
  echo ("MAC_ERROR: $packet");
  return true;
}
  
function cbDisconnect ($reason, $message, $language)
{
  die ("DISCONNECT: $message");
}