Why does inserting a Firestore document in PHP on XAMPP trigger an ERR_CONNECTION_RESET error?

Below is a list of potential issues and solutions to consider when you see an ERR_CONNECTION_RESET error during a write operation to Firestore:

1. TLS and cURL / OpenSSL Versions

Firestore endpoints require a secure TLS connection (typically TLS 1.2 or later). Although your test with file_get_contents('https://www.google.com') works, the Firebase PHP library may use cURL or another HTTP client that relies on your PHP/OpenSSL installation. If you’re using XAMPP, it’s possible that your cURL/OpenSSL version is outdated or misconfigured. 
Solution:

• Ensure that your XAMPP installation is up-to-date.
• Check that OpenSSL and cURL are built with TLS 1.2 support.
• In your php.ini, verify that the appropriate extensions (openssl, curl) are enabled and up-to-date.

2. Environment and Credential Configuration

Even though you mention the access key is correct, consider checking how the credentials are being loaded. If the credential file isn’t found or there is a subtle misconfiguration, the library might fail when making an attempt to write data.
Solution:

• Double-check the location and permissions for your service account JSON file (often loaded via the GOOGLE_APPLICATION_CREDENTIALS environment variable or through your application’s configuration).
• If your project uses dependency injection (as it appears with app('firebase.firestore')), make sure that the configuration for Firestore is properly set when creating the client.

3. Network or Server Inconsistencies

Even though you mention the firewall is disabled, sometimes local environments have other network security settings or issues with persistent connections.
Solution:

• Try testing the write operation from another network or machine to see if the issue persists.
• If possible, add logging around the insertion to capture more detailed error messages (the Firebase PHP library might offer additional logging features).

4. Debugging and Verbose Logging

Enable verbose logging in your HTTP client (if supported by your Firebase client library) to capture details about the SSL handshake or connection reset.
Example (if using cURL options indirectly):

PHPCopied
$options = [
    CURLOPT_VERBOSE => true,
    // Optionally capture the verbose log:
    CURLOPT_STDERR => fopen('php://stderr', 'w'),
];

$stuRef = $firestore->collection('users')->newDocument();
$stuRef->set([
    'email' => 'test2@test.ru',
    'password' => 'test2'
], $options);

(Note: The above example is schematic. Check your client library’s documentation on how to pass HTTP options or enable logging.)

Summary

The ERR_CONNECTION_RESET error during a Firestore data write likely points to underlying connection issues, particularly related to TLS support or environment configuration on your local XAMPP setup. Review your PHP and OpenSSL versions, ensure that credentials are properly configured, and if possible enable more detailed connection logs. These steps should help pinpoint and resolve the issue.