docs: add protocol-relative link to PHPDocs

Author: kenjis

system/HTTP/SiteURI.php

@@ -369,8 +369,10 @@ protected function applyParts(array $parts): void
     /**
      * For base_url() helper.
      *
-     * @param array|string $relativePath URI string or array of URI segments
-     * @param string|null  $scheme       URI scheme. E.g., http, ftp
+     * @param array|string $relativePath URI string or array of URI segments.
+     * @param string|null  $scheme       URI scheme. E.g., http, ftp. If empty
+     *                                   string '' is set, a protocol-relative
+     *                                   link is returned.
      */
     public function baseUrl($relativePath = '', ?string $scheme = null): string
     {
@@ -406,9 +408,11 @@ private function stringifyRelativePath($relativePath): string
     /**
      * For site_url() helper.
      *
-     * @param array|string $relativePath URI string or array of URI segments
-     * @param string|null  $scheme       URI scheme. E.g., http, ftp
-     * @param App|null     $config       Alternate configuration to use
+     * @param array|string $relativePath URI string or array of URI segments.
+     * @param string|null  $scheme       URI scheme. E.g., http, ftp. If empty
+     *                                   string '' is set, a protocol-relative
+     *                                   link is returned.
+     * @param App|null     $config       Alternate configuration to use.
      */
     public function siteUrl($relativePath = '', ?string $scheme = null, ?App $config = null): string
     {

system/Helpers/url_helper.php

@@ -23,9 +23,11 @@
     /**
      * Returns a site URL as defined by the App config.
      *
-     * @param array|string $relativePath URI string or array of URI segments
-     * @param string|null  $scheme       URI scheme. E.g., http, ftp
-     * @param App|null     $config       Alternate configuration to use
+     * @param array|string $relativePath URI string or array of URI segments.
+     * @param string|null  $scheme       URI scheme. E.g., http, ftp. If empty
+     *                                   string '' is set, a protocol-relative
+     *                                   link is returned.
+     * @param App|null     $config       Alternate configuration to use.
      */
     function site_url($relativePath = '', ?string $scheme = null, ?App $config = null): string
     {
@@ -42,8 +44,10 @@ function site_url($relativePath = '', ?string $scheme = null, ?App $config = nul
      * Returns the base URL as defined by the App config.
      * Base URLs are trimmed site URLs without the index page.
      *
-     * @param array|string $relativePath URI string or array of URI segments
-     * @param string|null  $scheme       URI scheme. E.g., http, ftp
+     * @param array|string $relativePath URI string or array of URI segments.
+     * @param string|null  $scheme       URI scheme. E.g., http, ftp. If empty
+     *                                   string '' is set, a protocol-relative
+     *                                   link is returned.
      */
     function base_url($relativePath = '', ?string $scheme = null): string
     {