Update PHP versions for Travis

.travis.yml

@@ -3,8 +3,10 @@ language: php
 
 # Versions of PHP to test against
 php:
-  - 5.4
+  - 5.6
+  - 7.1
   - 7.2
+  - 7.3
 
 env:
   global:
@@ -19,13 +21,14 @@ env:
 # Use PHPUnit 6 instead of PHPUnit 7 which Travis loads by default
 # with PHP 7.2. WordPress doesn't support PHPUnit 7.
 before_script:
-  - if [[ "$TRAVIS_PHP_VERSION" == "7.2" ]]; then wget -O phpunit https://phar.phpunit.de/phpunit-6.phar; fi
+  - if [[ "$TRAVIS_PHP_VERSION" == "7.2" ]]; then wget -O phpunit https://phar.phpunit.de/phpunit-7.phar; fi
+  - if [[ "$TRAVIS_PHP_VERSION" == "7.3" ]]; then wget -O phpunit https://phar.phpunit.de/phpunit-7.phar; fi
   - if [[ "$TRAVIS_PHP_VERSION" == "7.2" ]]; then chmod a+x phpunit; fi
+  - if [[ "$TRAVIS_PHP_VERSION" == "7.3" ]]; then chmod a+x phpunit; fi
   - bash bin/install-wp-tests.sh wordpress_test root '' localhost $WP_VERSION
 
 script:
-  - if [[ "$TRAVIS_PHP_VERSION" != "7.2" ]]; then phpunit; fi
-  - if [[ "$TRAVIS_PHP_VERSION" == "7.2" ]]; then ./phpunit; fi
+  - ./phpunit
 
 # Reduce mail notifications by Travis CI to a minimum
 notifications: