Following the tutorial Simfony (known PHP Framework) to the preliminary pre-requisite, reflected the lack of XSL module under Apache and PHP. Specifically, the message I found was:

[[WARNING]] XSL module is installed: FAILED
*** Install the XSL module (recommended for Propel) ***

The workaround is to install apt-get the missing modules as follows:

sudo apt-get install libapache2-modxslt php5-xsl

then restart the instance of Apache2

sudo / etc/init.d/apache2 restart

Restarting the configuration check the error message should be gone.