[BUGFIX] Prevent PHP deprecation in getCookieName()

Resolves: #103182
Releases: main, 12.4
Change-Id: If16e37c638a07e3afbb59d665141cc2ade583f4d
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/83083


Tested-by: core-ci <typo3@b13.com>
Tested-by: Oliver Bartsch <bo@cedev.de>
Tested-by: Andreas Kienast <a.fernandez@scripting-base.de>
Reviewed-by: Oliver Klee <typo3-coding@oliverklee.de>
Reviewed-by: Andreas Kienast <a.fernandez@scripting-base.de>
Tested-by: Oliver Klee <typo3-coding@oliverklee.de>
Reviewed-by: Oliver Bartsch <bo@cedev.de>

typo3/sysext/core/Classes/Authentication/BackendUserAuthentication.php

@@ -1810,18 +1810,12 @@ class BackendUserAuthentication extends AbstractUserAuthentication
     }
 
     /**
-     * Getter for the cookie name
-     *
-     * @static
-     * @return string returns the configured cookie name
+     * Returns the configured cookie name
      */
-    public static function getCookieName()
+    public static function getCookieName(): string
     {
-        $configuredCookieName = trim($GLOBALS['TYPO3_CONF_VARS']['BE']['cookieName']);
-        if (empty($configuredCookieName)) {
-            $configuredCookieName = 'be_typo_user';
-        }
-        return $configuredCookieName;
+        $configuredCookieName = trim((string)($GLOBALS['TYPO3_CONF_VARS']['BE']['cookieName'] ?? ''));
+        return $configuredCookieName !== '' ? $configuredCookieName : 'be_typo_user';
     }
 
     /**

typo3/sysext/frontend/Classes/Authentication/FrontendUserAuthentication.php

@@ -163,16 +163,11 @@ class FrontendUserAuthentication extends AbstractUserAuthentication
 
     /**
      * Returns the configured cookie name
-     *
-     * @return string
      */
-    public static function getCookieName()
+    public static function getCookieName(): string
     {
-        $configuredCookieName = trim($GLOBALS['TYPO3_CONF_VARS']['FE']['cookieName']);
-        if (empty($configuredCookieName)) {
-            $configuredCookieName = 'fe_typo_user';
-        }
-        return $configuredCookieName;
+        $configuredCookieName = trim((string)($GLOBALS['TYPO3_CONF_VARS']['FE']['cookieName'] ?? ''));
+        return $configuredCookieName !== '' ? $configuredCookieName : 'fe_typo_user';
     }
 
     /**