[THRIFT-5760] Update minimal version of php
diff --git a/lib/php/test/Unit/BinarySerializerTest.php b/lib/php/test/Unit/BinarySerializerTest.php
index b97da74..744ca7a 100644
--- a/lib/php/test/Unit/BinarySerializerTest.php
+++ b/lib/php/test/Unit/BinarySerializerTest.php
@@ -31,7 +31,7 @@
  */
 class BinarySerializerTest extends TestCase
 {
-    public function setUp()
+    public function setUp(): void
     {
         $loader = new ThriftClassLoader();
         $loader->registerNamespace('ThriftTest', __DIR__ . '/../Resources/packages/php');