Fix wp-admin loading on legacy WordPress versions

Three issues prevented wp-admin from working on PHP 5.6:

1. template.php and media.php were replaced with empty stubs as a
   workaround for the WASM parser size limit. The real fix is to
   strip doc comments (which stripDocCommentsFromWpIncludes already
   does). Remove the stub replacement. Also preserve ?> tags during
   comment stripping — PHP's ?> closes PHP mode even inside //
   comments.

2. Old WordPress (< 3.7) uses relative paths in wp-admin scripts.
   Patch these to use dirname(__FILE__) for absolute resolution.
   Covers index.php, index-extra.php, and admin.php across all
   old WP versions.

3. Auth cookies don't persist correctly for old WordPress admin
   sessions. Fix by re-generating auth cookies on every admin
   request: mu-plugin for WP 2.8+, direct admin.php patch for
   WP < 2.8 (no mu-plugin support). Handles three auth eras:
   - WP 2.5+: wp_generate_auth_cookie + $_COOKIE population
   - WP 2.0-2.4: USER_COOKIE/PASS_COOKIE with md5(md5(password))
   - WP 1.5: COOKIEHASH-based hardcoded cookie names

Also skip prefetchUpdateChecks for WP < 5.0 (the functions it
calls don't exist in old WP), skip 0-playground.php mu-plugin
for WP < 3.0 (closures in hooks cause fatal errors), and set up
wp_user_roles + usermeta when missing after install.

Author: JanJakes

packages/playground/client/src/blueprints-v1-handler.ts

@@ -87,10 +87,14 @@ export class BlueprintsV1Handler {
 
 		/**
 		 * Pre-fetch WordPress update checks to speed up the initial wp-admin load.
+		 * Skip for old WordPress versions — the functions called by prefetch
+		 * (wp_check_php_version, wp_update_plugins, etc.) don't exist or crash
+		 * on legacy WP, and the resulting PHP errors create noise.
 		 *
 		 * @see https://github.com/WordPress/wordpress-playground/pull/2295
 		 */
-		if (runtimeConfiguration.networking) {
+		const wpMajor = parseFloat(runtimeConfiguration.wpVersion) || 99;
+		if (runtimeConfiguration.networking && wpMajor >= 5) {
 			await playground.prefetchUpdateChecks();
 		}
 

packages/playground/remote/src/lib/playground-mu-plugin/0-playground.php

@@ -1,4 +1,11 @@
 <?php
+// WordPress < 3.0 can't handle closures as hook callbacks — the old
+// $wp_filter array structure uses string-indexed arrays internally
+// and treats Closure objects as arrays, causing fatal errors. Skip
+// this mu-plugin entirely for those ancient versions.
+if (isset($GLOBALS['wp_version']) && version_compare($GLOBALS['wp_version'], '3.0', '<')) {
+	return;
+}
 
 /**
  * Add a notice to wp-login.php offering the username and password.