In addition to the last post (13 years ago) from Dennis K. I corrected two typos (constant SSH2_STREAM_STDIO was misspellt) and removed (too many) brackets - this code works:
<?php
$stdout_stream = ssh2_exec($connection, "lsssss -la");
$sio_stream = ssh2_fetch_stream($stdout_stream, SSH2_STREAM_STDIO);
$err_stream = ssh2_fetch_stream($stdout_stream, SSH2_STREAM_STDERR);
stream_set_blocking($sio_stream, true);
stream_set_blocking($err_stream, true);
$result_dio = stream_get_contents($sio_stream);
$result_err = stream_get_contents($err_stream);
echo 'stderr: ' . $result_err;
echo 'stdio : ' . $result_dio;
?>
