Example of using the ssh2.sftp:// stream from the ssh2 pecl extension

pecl_ssh2_stream.php

<?php declare(strict_types=1);
// Tested on
// PHP 7.4.14 (cli) (built: Jan  5 2021 15:12:29) ( ZTS Visual C++ 2017 x64 )
// Windows 10 Pro
// pecl ssh2 v1.2

// Remote server
// Gentoo GNU/Linux Base System release 2.7

error_reporting(E_ALL);
ini_set('display_errors', '1');

file_put_contents(__DIR__.'/sftp.test', 'worked!');

$host = '10.5.6.254';
$port = 22;

$connection = ssh2_connect($host, $port);

if(!is_resource($connection)) {
    throw new Exception('Connection failed.');
}

// Without the __DIR__ php will just try to get 'id_rsa' and will fail.
// if your keys are elsewhere __DIR__ should be changed to C:\path\to\your\files
$privateKey = __DIR__.'\id_rsa_test'; // id_rsa
$publicKey = __DIR__.'\id_rsa_test.pub'; // id_rsa.pub
$username = 'eric';
$passphrase = 'passphrase'; // set this to passphrase if you have one.

$errorHandler = static function(
    int $errorNumber,
    string $errorString,
    string $errorFile = '',
    int $errorLine = 0,
    array $errorContext = []
) use($connection) {
    ssh2_disconnect($connection);
    var_dump($errorContext);
    throw new ErrorException($errorString, $errorNumber, 1, $errorFile, $errorLine);
};

set_error_handler($errorHandler);

if(false === ssh2_auth_pubkey_file($connection, $username, $publicKey, $privateKey, $passphrase)) {
    throw new Exception('Authentication failed.');
}

$sftp = ssh2_sftp($connection);
$remoteFile = '/home/eric/sftp.test';

$streamUrl = sprintf('ssh2.sftp://%d%s', (int)$sftp, $remoteFile);
$localFile = __DIR__ . '/sftp.test';

if(!file_exists($streamUrl)) {
    if(true === copy($localFile, $streamUrl)) {
        print sprintf('Successfully copied local file "%s" to remote file "%s"', $localFile, $streamUrl) . PHP_EOL;
    } else {
        print sprintf('Failed to copy local file %s to remote file %s', $localFile, $streamUrl) . PHP_EOL;
    }
} else {
    print sprintf('File %s exists.', $streamUrl) . PHP_EOL;
}

ssh2_disconnect($sftp);
ssh2_disconnect($connection);