Set cron job for absolute path
wget --spider 'http://www.xyz.com/controllera/functiona'
/usr/bin/php /path/to/index.php controller/method
wget http://www.xyz.com/controllera/functiona
# run everyday at 3 pm a GET HTTP request
0 15 * * * /usr/bin/wget http://www.xyz.com/controllera/functiona