Using better cache syntax

Author: Nyholm

bundles/best_practices.rst

@@ -217,8 +217,8 @@ test latest beta release. Here is a recommended configuration file (``.travis.ym
 
     before_install:
         - if [[ $COVERAGE != true ]]; then phpenv config-rm xdebug.ini || true; fi
-        - if [[ -v $STABILITY ]]; then composer config minimum-stability $STABILITY; fi;
-        - if [[ -v $DEPENDENCIES ]]; then composer require --no-update $DEPENDENCIES; fi;
+        - if ! [ -z "$STABILITY" ]; then composer config minimum-stability ${STABILITY}; fi;
+        - if ! [ -v $DEPENDENCIES ]; then composer require --no-update ${DEPENDENCIES}; fi;
 
     install:
         # To be removed when this issue will be resolved: https://github.com/composer/composer/issues/5355