Run tests on PHP 7.4 and simplify test matrix

.travis.yml

@@ -1,16 +1,5 @@
 language: php
 
-php:
-# - 5.3 # requires old distro, see below
-  - 5.4
-  - 5.5
-  - 5.6
-  - 7.0
-  - 7.1
-  - 7.2
-  - 7.3
-  - hhvm # ignore errors, see below
-
 # lock distro so new future defaults will not break the build
 dist: trusty
 
@@ -19,8 +8,17 @@ matrix:
     - php: 5.3
       dist: precise
       install: composer remove react/mysql --dev --no-interaction # do not install react/mysql example on legacy PHP
+    - php: 5.4
+    - php: 5.5
+    - php: 5.6
+    - php: 7.0
+    - php: 7.1
+    - php: 7.2
+    - php: 7.3
+    - php: 7.4
+    - php: hhvm-3.18
   allow_failures:
-    - php: hhvm
+    - php: hhvm-3.18
 
 sudo: false
 

tests/Io/FunctionsTest.php

@@ -47,6 +47,10 @@ public function testFdsWithInvalidPathReturnsSubsetOfFdsFromDevFd()
             $this->markTestSkipped('Unable to read /dev/fd');
         }
 
+        if (defined('HHVM_VERSION')) {
+            $this->markTestSkipped('Not supported on HHVM');
+        }
+
         $fds = Io\fds();
         $second = Io\fds('/dev/null');