Write PHP versions as strings

nicwortel · nicwortel · commit 3e70501bf87f · 2019-05-09T10:16:04.000+02:00
diff --git a/.travis.yml b/.travis.yml
@@ -5,8 +5,8 @@ branches:
 language: php
 
 php:
-  - 7.1
-  - 7.2
+  - '7.1'
+  - '7.2'
 
 matrix:
   include:
