[VENDOR] Pin to php-5.6-compatible versions
[VENDOR] Pin to php-5.6-compatible versions

Signed-off-by: Olivier Mehani <9858fe98d2c7f5f35e0d2a08f134cfc58afd42d3@learnosity.com>

Learnosity/learnosity-sdk-php,Learnosity/learnosity-sdk-php