Optimize HTML cache pipeline for minimum latency and maximum throughput (PHP 8.3+)

[Copilot]

The HTML cache drop-in lacked pre-compressed serving, critical HTTP caching headers, and several correctness issues that left performance and browser/CDN cacheability on the table. The cache lifetime was also hardcoded at 3600 s in the drop-in, ignoring the admin setting.

advanced-cache-template.php — hot path (every cached request)

• Pre-compressed gzip serving: serves index.html.gz directly when Accept-Encoding: gzip is present and the file exists, eliminating per-request compression CPU entirely. Disables zlib.output_compression to prevent double-encoding.
• Full HTTP caching headers: adds Last-Modified, Expires, Content-Length, Vary: Accept-Encoding.
• If-Modified-Since support: 304 on date-based conditional GETs, not just ETag. Fixed comparison to < (not <=).
• Apache-style ETag: "<hex-mtime>-<hex-size>" — includes file size so same-second rewrites invalidate correctly.
• Runtime config: reads WPSC_CACHE_DIR/config.php (written by plugin on activation/save) so cache_lifetime tracks the admin setting.
• PHP 8.3 typed class constants; str_starts_with / str_contains / str_ends_with; is_file() over file_exists(); parse_url false-safety (?: not ??).

HTMLCache.php — write path (once per uncached request)

• Writes .html.gz alongside .html: gzencode($content, 6) via atomicWrite, so the drop-in always has a pre-compressed sibling to serve.
• HTML minification: strips non-conditional HTML comments and collapses inter-tag whitespace runs. Applied after all other processors. preg_replace null-return guarded to avoid content corruption on invalid UTF-8.
• text/html content-type guard: skips caching JSON/XML/REST responses.
• Fix libxml_use_internal_errors leak: saves and restores previous state; was permanently silencing libxml errors for the remainder of the request.
• PHP 8.3 typed class constants on BYPASS_PARAMS, MAX_QUERY_LEN, IGNORED_EXTENSIONS.

AbstractCacheDriver.php

• LOCK_EX added to file_put_contents in atomicWrite for safer concurrent writes.

Plugin.php

• installAdvancedCache() always overwrites: was a no-op after first install, silently leaving a stale drop-in after plugin updates.
• writeAdvancedCacheConfig(): serialises ['cache_lifetime' => N] to WPSC_CACHE_DIR/config.php using var_export + LOCK_EX. Called on activation and on wpscac_settings_updated → refreshServerConfig(). Logs failure under WP_DEBUG.

Original prompt

Please find out if the current workflow gives us the best possible html/documentation latency html cache speed possible, for best latency and maximum troughput for cached websites.
Try to optimized the code aswell and find issues in that files/area around this topic. Use php 8.3+ newest optimizations and so on to give the msot performant code possible here

The user has attached the following file paths as relevant context:

• WPS-Cache\includes\advanced-cache-template.php
• WPS-Cache\src\Plugin.php
• WPS-Cache\wps-cache.php
• WPS-Cache\src\Cache\Drivers\HTMLCache.php

Created from VS Code.

---

💡 You can make Copilot smarter by setting up custom instructions, customizing its development environment and configuring Model Context Protocol (MCP) servers. Learn more Copilot coding agent tips in the docs.