Handle PHP upload size limits gracefully

[codeling]

Improve handling of file uploads that exceed PHP's upload_max_filesize and post_max_size limits by detecting these conditions and showing user-friendly error messages instead of generic security token errors.

Changes

• Detection of oversized requests: Added check in index.php to detect when POST requests exceed post_max_size (indicated by missing $_POST and $_FILES despite non-zero CONTENT_LENGTH), returning HTTP 413 with a clear message naming the limit
• Detection of oversized files: Added check for UPLOAD_ERR_INI_SIZE and UPLOAD_ERR_FORM_SIZE PHP upload errors, showing a message with the upload_max_filesize limit
• Improved error messaging: Removed misleading "uploaded file too large" text from the generic security token error message, since oversized uploads are now handled separately
• Documentation: Added section to INSTALL.md explaining PHP upload limits and how to configure web server limits (nginx client_max_body_size, Apache LimitRequestBody) to work together
• Internationalization: Added German and English translations for the new error messages
• Test infrastructure: Extended AppServer to support setting PHP ini values via phpIni option in server configuration
• Integration tests: Added UploadSizeLimitTest with four test cases covering:
  • Files exceeding upload_max_filesize (40K limit)
  • Requests exceeding post_max_size (100K limit)
  • Successful uploads within limits
  • Security token validation still enforced for normal requests

Implementation details

The solution distinguishes between two size limit scenarios:

1. Single file too large (upload_max_filesize): PHP sets $_FILES['userfile']['error'] to UPLOAD_ERR_INI_SIZE or UPLOAD_ERR_FORM_SIZE
2. Entire request too large (post_max_size): PHP discards the entire request body, leaving $_POST and $_FILES empty despite CONTENT_LENGTH being set

Both cases now provide specific, actionable error messages to users rather than confusing them with security token errors.

https://claude.ai/code/session_01Ahgn25kLAXMcG4V7N6s6u9