Fix build for PHP 5.4, 5.5

Author: geekwright

.travis.yml

@@ -1,8 +1,6 @@
 language: php
 
 php:
-  - 5.4
-  - 5.5
   - 5.6
   - 7.0
   - 7.1
@@ -14,6 +12,10 @@ matrix:
   include:
     - php: 5.3
       dist: precise
+    - php: 5.4
+      dist: trusty
+    - php: 5.5
+      dist: trusty
   allow_failures:
     - php: nightly
     - php: 7.4snapshot