; rel=preload; as=%s', esc_url(self::http2LinkUrlToRelativePath($preload_src)), sanitize_html_class(self::http2LinkResourceHintAs(current_filter(), $preload_src)) ); $headerAsString = implode(' ', headers_list()); // +2 comes from the last CRLF since it's two bytes $headerSize = strlen($headerAsString) + strlen($newHeader) + 2; // If the current header size is larger than $maxHeaderSize bytes // ignore following resources which can be pushed // This is a workaround for Cloudflare's 8KiB header limit // and fastcgi default 4KiB header limit $maxHeaderSize = 3072; // 3 KiB by default if (defined('CLOUDFLARE_HTTP2_SERVER_PUSH_HEADER_SIZE')) { $maxHeaderSize = absint(CLOUDFLARE_HTTP2_SERVER_PUSH_HEADER_SIZE); }; if ($headerSize > $maxHeaderSize) { if (defined('CLOUDFLARE_HTTP2_SERVER_PUSH_LOG') && CLOUDFLARE_HTTP2_SERVER_PUSH_LOG) { error_log("Cannot Server Push (header size over $maxHeaderSize bytes)."); } return $src; } header($newHeader, false); $GLOBALS['http2_'.self::http2LinkResourceHintAs(current_filter(), $preload_src).'_srcs'][] = self::http2LinkUrlToRelativePath($preload_src); } } return $src; } /** * Render "resource hints" in the section of the page. These encourage preload/prefetch behavior * when HTTP/2 support is lacking. */ public static function http2ResourceHints() { $resource_types = array('script', 'style'); array_walk($resource_types, function ($resource_type) { $key = "http2_{$resource_type}_srcs"; if (isset($GLOBALS[$key]) && is_array($GLOBALS[$key])) { array_walk($GLOBALS[$key], function ($src) use ($resource_type) { printf('', esc_url($src), esc_html($resource_type)); }); } }); } /** * Convert an URL with authority to a relative path. * * @param string $src URL * * @return string mixed relative path */ public static function http2LinkUrlToRelativePath($src) { return '//' === substr($src, 0, 2) ? preg_replace('/^\/\/([^\/]*)\//', '/', $src) : preg_replace('/^http(s)?:\/\/[^\/]*/', '', $src); } /** * Maps a WordPress hook to an "as" parameter in a resource hint. * * @param string $current_hook pass current_filter() * * @return string 'style' or 'script' */ public static function http2LinkResourceHintAs($current_hook, $src) { switch ($current_hook) { case 'style_loader_src': return 'style'; case 'script_loader_src': return 'script'; case 'autoptimize_filter_cache_getname': $ext = pathinfo($src, PATHINFO_EXTENSION); if ($ext === 'js') { return 'script'; } elseif ($ext === 'css') { return 'style'; } return ''; default: return ''; } } }