Fix deprecations warning on PHP 8.4 (#282)

* Add `nullable_type_declarations` rule

* Apply fixes from StyleCI

---------

Co-authored-by: StyleCI Bot <bot@styleci.io>

Author: crynobone

.styleci.yml

@@ -1,4 +1,6 @@
 php:
   preset: laravel
+  enabled:
+    - nullable_type_declarations
 js: true
 css: true

src/ParallelSSH.php

@@ -16,7 +16,7 @@ class ParallelSSH extends RemoteProcessor
      * @param  \Closure|null  $callback
      * @return int
      */
-    public function run(Task $task, Closure $callback = null)
+    public function run(Task $task, ?Closure $callback = null)
     {
         $processes = [];
 

src/RemoteProcessor.php

@@ -17,7 +17,7 @@ abstract class RemoteProcessor
      * @param  \Closure|null  $callback
      * @return int
      */
-    abstract public function run(Task $task, Closure $callback = null);
+    abstract public function run(Task $task, ?Closure $callback = null);
 
     /**
      * Run the given script on the given host.

src/SSH.php

@@ -15,7 +15,7 @@ class SSH extends RemoteProcessor
      * @param  \Closure|null  $callback
      * @return int
      */
-    public function run(Task $task, Closure $callback = null)
+    public function run(Task $task, ?Closure $callback = null)
     {
         $processes = [];