Fix syntax error when using a trailing ampersand

Author: zborboa-g

.travis.yml

@@ -10,7 +10,7 @@ matrix:
     - php: 5.6
     - php: hhvm
 before_script:
-  - if [[ "$TRAVIS_PHP_VERSION" != "5.3" ]]; then php -S 127.0.0.1:8000 -t tests/PHPCurlClass/ &; fi
+  - if [[ "$TRAVIS_PHP_VERSION" != "5.3" ]]; then sh -c "php -S 127.0.0.1:8000 -t tests/PHPCurlClass/ &"; fi
 script:
   - php -l src/*
   - if [[ "$TRAVIS_PHP_VERSION" != "5.3" ]]; then cd tests && phpunit --configuration phpunit.xml; fi