It's not easy getting APC to work on Travis-CI, every now and then something is updated and your clever solution is broken again. What's super annoying is that you cannot even trust the documentation. Right now it says that APC is available for PHP 7, but when you try to activate the extension a wild error message appears, saying the extension file is missing… Anyway, I searched the internet and here the solution I found.

Choosing the right extension, version

In order to have APC working for your PHP version, you actually need to install apcu, since apc has been abandoned in 2012. Also, you need to pick the right version, because v4.0 is only working up to PHP 5.6, while v5.0 is only working from PHP 7.0:

sudo: false

language: php

  - 5.6
  - 7.0

  - if [[ $TRAVIS_PHP_VERSION = "5.6" ]]; then echo yes | pecl install apcu-4.0.11; fi
  - if [[ $TRAVIS_PHP_VERSION = "7.0" ]]; then echo yes | pecl install apcu-5.1.5; fi
  - if [[ $TRAVIS_PHP_VERSION != "hhvm" ]]; then phpenv config-add .travis/travis-$TRAVIS_PHP_VERSION.ini; fi

Note: As you can see, this is compatible with the new container infrastructure.

Also, in a .travis folder (or whatever), add the corresponding files to enable the extension. For PHP 5.6 you need to create a corresponding travis-5.6.ini file:

apc.enable_cli = 1

You can check my Storage package's config for a real life example.

Ariadne's thread