I should note that libssh2 returns int from libssh2_sftp_readdir() in the earliest version I can find of the library, so this should not be a problem for backward compatibility.

I recreated this issue with libssh2-1.2.9 and a GlobalSCAPE Secure FTP Server (v3.3.1 Build 04.28.2008.1).

To recreate, you must have a large number of files in the remote directory (We ran into it with 160 files in the directory, or with even less in older versions of libssh2. FileZilla 3.3.1 is not able to list the contents of the directory either, but at least does not segfault.):

        // change these as needed
        $host = '123.123.123.123';
        $port = '22';
        $username = 'username';
        $password = 'password';
        $dir = '/';

        $res = ssh2_connect( $host, $port );
        if( !$res )
                throw new Exception( 'Could not connect to server.' );
        ssh2_auth_password( $res, $username, $password );

        echo ssh2_fingerprint($res).PHP_EOL;

        $sftp = ssh2_sftp($res);
        if( !$sftp )
                throw new Exception( 'Could not open sftp stream in ssh session' );

        $dir = ssh2_sftp_realpath( $sftp, $path );
        if( !$dir )
                throw new Exception( 'bad path (1)' );

        $resource_path = 'ssh2.sftp://' . $sftp . $dir;
        $dp = opendir( $resource_path );
        if( !$dp )
                throw new Exception( 'bad path (2)' );

        $retval = array();
        while( FALSE !== ($file = readdir($dp)) )
        {
                if( $file{0} == '.' || $file == '..' )
                        continue;
                $fp = $dir . (substr($dir,strlen($dir)-1,1) == '/' ? '' : '/') . $file;
                $file_path = ssh2_sftp_realpath( $sftp, $fp ); // SEGFAULT HERE WHEN TESTING WITH THE SPECIFIED CONDITIONS
        }