The "pty" parameter is not documented.

You should pass a pty emulation name ("vt102", "ansi", etc...) if you want to emulate a pty, or NULL if you don't.

Passing false will convert false to a string, and will allocate a "" terminal.

There doesn't appear to be a way to get data from BOTH stderr and stdout streams simultaneously, or at least I've yet to find one.

The following code *should* get the error message written to stderr, but if the call to stream_get_contents() for stdout is run first, the subsequent call for stderr won't return anything.  

If the order of the statements is reversed, the call for stderr will return any errors and call for stdout will return nothing

<?php
// Run a command that will probably write to stderr (unless you have a folder named /hom)
$stream = ssh2_exec($connection, "cd /hom");
$errorStream = ssh2_fetch_stream($stream, SSH2_STREAM_STDERR);

// Enable blocking for both streams
stream_set_blocking($errorStream, true);
stream_set_blocking($stream, true);

// Whichever of the two below commands is listed first will receive its appropriate output.  The second command receives nothing
echo "Output: " . stream_get_contents($stream);
echo "Error: " . stream_get_contents($errorStream);

// Close the streams        
fclose($errorStream);
fclose($stream);

?>

My initial suspicion is that either a) I've done something wrong  or b) the blocking nature of both streams means that by the time first stream has received data and returned, the buffer for the second stream has already emptied.

I've done preliminary tests with blocking disabled, but haven't had any luck there either.

The following function can be used to read both stdout and stderr even if both streams contain gigabytes of data. It solves most problems mentioned in other comments, like blocking, like further using the existing connection etc.

  function ssh2_run($ssh2,$cmd,&$out=null,&$err=null){
    $result=false;
    $out='';
    $err='';
    $sshout=ssh2_exec($ssh2,$cmd);
    if($sshout){
      $ssherr=ssh2_fetch_stream($sshout,SSH2_STREAM_STDERR);
      if($ssherr){
        # we cannot use stream_select() with SSH2 streams
        # so use non-blocking stream_get_contents() and usleep()
        if(stream_set_blocking($sshout,false) and
           stream_set_blocking($ssherr,false)
        ){
          $result=true;
          # loop until end of output on both stdout and stderr
          $wait=0;
          while(!feof($sshout) or !feof($ssherr)){
            # sleep only after not reading any data
            if($wait)usleep($wait);
            $wait=50000; # 1/20 second
            if(!feof($sshout)){
              $one=stream_get_contents($sshout);
              if($one===false){ $result=false; break; }
              if($one!=''){ $out.=$one; $wait=0; }
            }
            if(!feof($ssherr)){
              $one=stream_get_contents($ssherr);
              if($one===false){ $result=false; break; }
              if($one!=''){ $err.=$one; $wait=0; }
            }
          }
        }
        # we need to wait for end of command
        stream_set_blocking($sshout,true);
        stream_set_blocking($ssherr,true);
        # these will not get any output
        stream_get_contents($sshout);
        stream_get_contents($ssherr);
        fclose($ssherr);
      }
      fclose($sshout);
    }
    return $result;
  }

Here's what I use for doing ssh2_exec for long running scripts, expanding on other examples.  It waits for a timeout and checks if both streams are finished.  Does not use blocking and it gets data from both STDOUT and STDERR.

<?php
$stdout = ssh2_exec($ssh, $cmd);
$stderr = ssh2_fetch_stream($stdout, SSH2_STREAM_STDERR);
if (!empty($stdout)) {

    $t0 = time();
    $err_buf = null;
    $out_buf = null;

    // Try for 30s
    do {

        $err_buf.= fread($stderr, 4096);
        $out_buf.= fread($stdout, 4096);

        $done = 0;
        if (feof($stderr)) {
            $done++;
        }
        if (feof($stdout)) {
            $done++;
        }

        $t1 = time();
        $span = $t1 - $t0;

        // Info note
        echo "while (($tD < 20) && ($done < 2));\n";

        // Wait here so we don't hammer in this loop
        sleep(1);

    } while (($span < 30) && ($done < 2));

    echo "STDERR:\n$err_buf\n";
    echo "STDOUT:\n$out_buf\n";

    echo "Done\n";

} else {
    echo "Failed to Shell\n";
}
?>

Adjust your timeout as necessary.

I believe most of the problem that people are having here is that there is a misconception about what blocking *really* means.

Blocking means a read from the *stream* will wait until there is data.  Not necessarily all the data from the application -- but *some*.  So it won't help you at all if you're executing a command that doesn't write to stdout, or writes a whole lot of data.

So there are 2 problems:

1. If you need to know that a silent program is done via ssh2_exec, you'll need to signal it to yourself.  ssh2_exec will *not* block execution until the command is done executing.  And 2 consecutive ssh2_execs may execute asynchronously.  You could also log into a shell via ssh2_shell and parse up to the next prompt -- but that's overkill.  You can also do this by adding on some sort of sentinel at the end of your command, such as echo "@," and then block on reads until you see a "@."  Ensure "@" won't appear in the output, or escape the output via some encoding mechanism if you can't do that.

2. If the program takes awhile, you have the same problem.  You need to read until you're done.  So you need a sentinel value like the above.

3. Sleep() is just a bad idea here.  Commands rarely take the same amount of time to execute a command twice.  It may be OK if you're doing *one* thing and can just wait 5 seconds.  But that's not cool if it's something you're doing in a loop.

Hope this helps!

Executing remote Windows commands...
After some hair pulling, I thought I'd suggest a couple things that might help others:

1. Use 'ssh2_fetch_stream' to open a stderr stream according to the manual.
2. Windows shell commands require 'cmd /C [command]' to execute.  (I had forgotten this)

<?php
    // code fragment
    $stdout_stream = ssh2_exec($connection, 'cmd /C dir');
    $stderr_stream = ssh2_fetch_stream($stdout_stream, SSH2_STREAM_STDERR);
?>

I didn't realize the need for the 'cmd /C' until I saw the stderr response 'dir: not found'.

It is also good to use register_shutdown_function to shred the keys after this runs.

if you are using exec function, and have problems with a output > 1000 lines
you should use  

<?php
                stream_set_blocking($stream, true);
                while($line = fgets($stream)) {
                        flush();
                        echo $line."<br />";
                }
?>

except

<?php
                stream_set_blocking($stream, true);
               echo stream_get_contents($stream);
?>

Since version 0.13 of the SSH2 extension, it's possible to retrieve the command exit status with stream_get_meta_data().

For example:

<?php
$channel = ssh2_exec($connection, $command);

$metadata = stream_get_meta_data($channel);

$exitCode = $metadata['exit_status'];

?>

Retrieving the exit code is very helpful, since usually, commands return 0 in case of success, and other values in case of errors.

If you want to run many exec orders throught ssh2 in the same process using the same variable $stream for exemple and to read the output for each order, you must close the stream after each order else you will not be able to read the next order output.

<?php
 $stream=ssh2_exec($conn_id,"/usr/bin/ls .");
    stream_set_blocking( $stream, true );
    $cmd=fread($stream,4096);
fclose($stream);

if(ereg("public_html",$cmd)){
 // ...........................................
}

 $stream=ssh2_exec($conn_id,"/usr/bin/ls public_html");
    stream_set_blocking( $stream, true );
    $cmd=fread($stream,4096);
fclose($stream);

if(ereg("images",$cmd)){
 // ..........................................
}

 
$stream=ssh2_exec($conn_id,"/usr/bin/ls public_html/images");
    stream_set_blocking( $stream, true );
    $cmd=fread($stream,4096);
fclose($stream);

if(ereg("blabla",$cmd)){
 // ..........................................
}
?>

This is the best way I found to automatically run multiple commands or commands that might take longer then expected.  NOTE: this assumes that no where in the output is there the text '[end]' otherwise the function will end prematurely.  Hope this helps people.

<?php
$ip = 'ip_address';
$user = 'username';
$pass = 'password';

$connection = ssh2_connect($ip);
ssh2_auth_password($connection,$user,$pass);
$shell = ssh2_shell($connection,"bash");

//Trick is in the start and end echos which can be executed in both *nix and windows systems. 
//Do add 'cmd /C' to the start of $cmd if on a windows system.
$cmd = "echo '[start]';your commands here;echo '[end]'";
$output = user_exec($shell,$cmd);

fclose($shell);

function user_exec($shell,$cmd) {
  fwrite($shell,$cmd . "\n");
  $output = "";
  $start = false;
  $start_time = time();
  $max_time = 2; //time in seconds
  while(((time()-$start_time) < $max_time)) {
    $line = fgets($shell);
    if(!strstr($line,$cmd)) {
      if(preg_match('/\[start\]/',$line)) {
        $start = true;
      }elseif(preg_match('/\[end\]/',$line)) {
        return $output;
      }elseif($start){
        $output[] = $line;
      }
    }
  }
}

?>

[EDIT BY danbrown AT php DOT net: Contains a bugfix supplied by (jschwepp AT gmail DOT com) on 17-FEB-2010 to fix a typo in a function name.]

Running multiple commands shows this warning and second(and any next) command wont be executed:
- PHP Warning:  ssh2_exec(): Unable to request a channel from remote host in ...

Solution with fclose($stream) does not work, but this is simple solution which works for me:

<?php

$connection = ssh2_connect('SOME SSH IP ADDRESS', 22);
ssh2_auth_password($connection, 'username', 'passwortd');

//those commands are for some HUAWEI enterprise routers

    $stream = ssh2_exec( $connection, "screen-length 0 temporary\ndisplay isis name-table" );
    stream_set_blocking( $stream, true );
    $stream_out = ssh2_fetch_stream( $stream, SSH2_STREAM_STDIO );
    echo stream_get_contents($stream_out);

?>

first command is: screen-length 0 temporary
second command is: display isis name-table
which is executed with \n in the same line.
You have to separete outputs of those commands later.

Looks like ssh2_exec allocates exec stream in session you are connected in, and for freeing it , you have to ssh2_disconnect. 
Usualy you are ok to ssh2_exec one command then disconnect, then connect and ssh2_exec next command. This is how some other php libraries works as I have seen. But sometimes some variables are sesion dependent, and when you disconnect variables resets.

If the ssh2_exec takes awhile to run, and you need a handshake, you can use a file.  In this case, $flag names a handshake file that is written when the ssh script finishes.

<?php
                $stream = ssh2_exec($connection, $command . " $public_key $private_key;");
                $i=0;
                while (!file_exists ($flag) && ($i < MAX_TIME))
                {
                        sleep(1);
                        $i++;
                }
                $ret_val=($stream!=FALSE);
?>

This is an extract out of the bash script that is running.  Be sure to allow the webserver permission to read the file that the script writes.

echo 0 > $OUTFILE
chmod 666 $OUTFILE

One other note:  you can put more than one command in by separating them with ';' (semicolons).

It is important to note that this will not work ~all~ hosts that allow SFTP. We deny shell access, but allow SFTP using the sftp-internal subsystem.

When attempting to use ssh2_exec() with this configuration, and stream_set_blocking set to true, the script will hang indefinitely. When stream_set_blocking is set to false, nothing will be returned.

Even if you can SFTP files, be sure to check with your host to see if you have shell access.

*** IMPORTANT ***
If you are having issues getting STDERR on PHP 5.2.X, make sure to update to 5.2.17 and latest ssh2 extension from PECL.

Oddly enough, I've noticed if I attempt to execute anything nothing happens. Now, I don't mean "No content is returned!".. I mean, "The command I told it to execute didn't execute!".

Unless the following pattern is followed:

<?php
$stream = ssh2_exec($connection, "touch ~/some_fake_file", 'xterm');
stream_get_contents($stream);
?>

Nowhere in the manual does it imply that stream_get_contents is required for the actual execution to take place, but in this case.. it seems that way. So, if you're having trouble getting commands to execute, try using stream_get_contents().

The command  may not finish before the function return if the stream is not set to blocking mode. You may have to set the stream to blocking mode in order to get any output from the command.

<?php
  // [Open connection]
  // ...

  $stream = ssh2_exec($connection, 'ps ax');
  stream_set_blocking($stream, true);
  
  // The command may not finish properly if the stream is not read to end
  $output = stream_get_contents($stream);
  
  // ...
  // [Close stream and connection]
?>