To enable error reporting in Apache/PHP, edit /etc/php5/apache2/php.ini

Code:
sudo subl /etc/php5/apache2/php.ini
Find

Code:
display_errors = Off
Replace with

Code:
display_errors = On
Find

Code:
error_reporting = E_ALL & ~E_DEPRECATED & ~E_STRICT
Replace with

Code:
error_reporting = E_ALL

Save and exit the file.

Now restart Apache

Code:
sudo service apache2 restart