remove id check when checking for started session

src/SessionManager.php

@@ -9,6 +9,8 @@
 
 use function array_key_exists;
 use function array_merge;
+use function constant;
+use function defined;
 use function headers_sent;
 use function is_array;
 use function iterator_to_array;
@@ -91,12 +93,19 @@ public function sessionExists()
             return true;
         }
 
-        if ($this->getId()) {
+        /**
+         * @var string|false $sid
+         */
+        $sid = defined('SID') ? constant('SID') : false;
+
+        if ($sid !== false && $this->getId()) {
             return true;
         }
+
         if (headers_sent()) {
             return true;
         }
+
         return false;
     }
 

test/SessionManagerTest.php

@@ -17,6 +17,7 @@
 use Laminas\Session\Validator\Id;
 use Laminas\Session\Validator\RemoteAddr;
 use LaminasTest\Session\TestAsset\Php81CompatibleStorageInterface;
+use PHPUnit\Framework\Attributes\RunInSeparateProcess;
 use PHPUnit\Framework\TestCase;
 use Traversable;
 
@@ -35,6 +36,7 @@
 use function session_write_close;
 use function set_error_handler;
 use function stristr;
+use function uniqid;
 use function var_export;
 use function xdebug_get_headers;
 
@@ -902,6 +904,29 @@ public function testIdValidationWillFailOnInvalidData(): void
         $this->manager->start();
     }
 
+    #[RunInSeparateProcess]
+    public function testSettingTheIdentifierBeforeStartingTheSessionYieldsTheExpectedId(): void
+    {
+        $manager = new SessionManager();
+
+        $id = uniqid();
+
+        $manager->setId($id);
+
+        // setting a session id does not mark a session as started
+        self::assertFalse($manager->sessionExists());
+
+        $manager->start();
+
+        self::assertTrue($manager->sessionExists());
+
+        $manager->writeClose();
+
+        // calling writeClose() does not mark the session as closed
+        self::assertTrue($manager->sessionExists());
+        self::assertSame($id, $manager->getId());
+    }
+
     /** @param non-empty-string $property */
     private function assertAttributeEquals(mixed $expected, string $property, object $object): void
     {