chore: add back timestamp var for compatibility (#412)

Author: bshaffer

src/JWT.php

@@ -41,6 +41,15 @@ class JWT
      */
     public static $leeway = 0;
 
+    /**
+     * Allow the current timestamp to be specified.
+     * Useful for fixing a value within unit testing.
+     * Will default to PHP time() value if null.
+     *
+     * @var ?int
+     */
+    public static $timestamp = null;
+
     /**
      * @var array<string, string[]>
      */
@@ -84,7 +93,7 @@ public static function decode(
         $keyOrKeyArray
     ): stdClass {
         // Validate JWT
-        $timestamp = \time();
+        $timestamp = \is_null(static::$timestamp) ? \time() : static::$timestamp;
 
         if (empty($keyOrKeyArray)) {
             throw new InvalidArgumentException('Key may not be empty');