[THRIFT-5760] Update minimal version of php
diff --git a/lib/php/test/Unit/JsonSerializeTest.php b/lib/php/test/Unit/JsonSerializeTest.php
index 9fdc3f3..66e4d5e 100644
--- a/lib/php/test/Unit/JsonSerializeTest.php
+++ b/lib/php/test/Unit/JsonSerializeTest.php
@@ -31,7 +31,7 @@
  */
 class JsonSerializeTest extends TestCase
 {
-    protected function setUp()
+    protected function setUp(): void
     {
         $loader = new ThriftClassLoader();
         $loader->registerNamespace('ThriftTest', __DIR__ . '/../Resources/packages/phpjs');