Undefined method ‘getStream’ SFTP

There is a file I want to read from another server via SFTP and .pem key.
I made connection to server and it was successful now when reading the file from server using this line

// Connect to SFTP
$sftp = new SFTP($host, $port);
if (!$sftp->login($username, $key)) {
    exit('Login Failed');
}

// Read a remote file
$remoteFile = '/path/to/file.log';
$content = $sftp->get($remoteFile);

I am getting below error.

Fatal error: Allowed memory size of 134217728 bytes exhausted (tried to allocate 98566176 bytes) in /var/www/Utility/vendor/phpseclib/phpseclib/phpseclib/Net/SFTP.php on line 2461

I tried the following code

$stream = $sftp->getStream('largefile.dat');
if ($stream) {
    while (!feof($stream)) {
        $chunk = fread($stream, 8192);
        // Process $chunk
    }
    fclose($stream);
}

But it gives the error

Undefined method ‘getStream’.intelephense(P1013)

I tried checking everything php phpseclib installation is proper.