Update cache output

advanced-cache.php

@@ -3,10 +3,6 @@ if (!isset($_SERVER['REQUEST_METHOD']) || $_SERVER['REQUEST_METHOD'] != 'GET') {
     return false;
 }
 
-if (!empty($_GET) && !isset($_GET['utm_source'], $_GET['utm_medium'], $_GET['utm_campaign'])) {
-    return false;
-}
-
 if (!empty($_COOKIE)) {
     foreach ($_COOKIE as $k => $v) {
         if (preg_match('/^(wp-postpass|wordpress_logged_in|comment_author)_/', $k)) {
@@ -16,45 +12,34 @@ if (!empty($_COOKIE)) {
 }
 
 $timeout_file = WP_CONTENT_DIR . '/advanced-cache/timeout';
-$expires_seconds = MINUTE_IN_SECONDS;
+$expires_seconds = 10 * MINUTE_IN_SECONDS;
 
-if (is_readable($timeout_file) && ($buffer = file_get_contents($timeout_file)) !== false) {
-    $expires_seconds = (int) $buffer * MINUTE_IN_SECONDS;
+if (is_readable($timeout_file) && filesize($timeout_file) > 0) {
+    $expires_seconds = abs(intval(file_get_contents($timeout_file))) * MINUTE_IN_SECONDS;
 }
 
-$expires_seconds = $expires_seconds >= MINUTE_IN_SECONDS ? $expires_seconds : MINUTE_IN_SECONDS;
+$expires_seconds = $expires_seconds >= (1 * MINUTE_IN_SECONDS) ? $expires_seconds : (10 * MINUTE_IN_SECONDS);
 
-$path = sprintf(
-    '%s%s%s%s',
-    WP_CONTENT_DIR . '/advanced-cache',
-    DIRECTORY_SEPARATOR,
-    parse_url('https://' . strtolower($_SERVER['HTTP_HOST']), PHP_URL_HOST),
-    parse_url($_SERVER['REQUEST_URI'], PHP_URL_PATH)
-);
+$path = WP_CONTENT_DIR . '/advanced-cache' .
+    DIRECTORY_SEPARATOR .
+    parse_url('https://' . strtolower($_SERVER['HTTP_HOST']), PHP_URL_HOST) .
+    parse_url($_SERVER['REQUEST_URI'], PHP_URL_PATH);
 
 $path = rtrim($path, '/\\') . '/';
 
-$path_html = $path . 'index.html';
-
-if (is_readable($path_html)
-    && ($buffer = file_get_contents($path_html)) !== false
-    && ((filemtime($path_html) + $expires_seconds) > time())) {
-    if (function_exists('apache_request_headers')) {
-        $headers = apache_request_headers();
-        $http_if_modified_since = isset($headers['If-Modified-Since']) ? $headers['If-Modified-Since'] : '';
-        $http_accept = isset($headers['Accept']) ? $headers['Accept'] : '';
-        $http_accept_encoding = isset($headers['Accept-Encoding']) ? $headers['Accept-Encoding'] : '';
-    } else {
-        $http_if_modified_since = isset($_SERVER['HTTP_IF_MODIFIED_SINCE']) ? $_SERVER['HTTP_IF_MODIFIED_SINCE'] : '';
-        $http_accept = isset($_SERVER['HTTP_ACCEPT']) ? $_SERVER['HTTP_ACCEPT'] : '';
-        $http_accept_encoding = isset($_SERVER['HTTP_ACCEPT_ENCODING']) ? $_SERVER['HTTP_ACCEPT_ENCODING'] : '';
-    }
+$cache_file = $path . 'index.html';
 
-    if ($http_if_modified_since && strtotime($http_if_modified_since) == filemtime($path_html)) {
-        header($_SERVER['SERVER_PROTOCOL'] . ' 304 Not Modified', true, 304);
+// Check if the cache file exists and is readable.
+if (is_readable($cache_file) && ($content = file_get_contents($cache_file)) !== false && (filesize($cache_file) > 0)) {
+    // Check if the cache file is not stale.
+    if (($filemtime = filemtime($cache_file) + $expires_seconds) > time()) {
+        // Not stale: Output the content of the cache file.
+        header('Last-Modified: ' . date('r', $filemtime), true);
+        header('Cache-Control: max-age=' . $expires_seconds . ', must-revalidate', true);
+        echo $content;
         exit;
+    } else {
+        // Stale: Remove the cache file.
+        unlink($cache_file);
     }
-
-    echo $buffer;
-    exit;
 }