Problem solved! Actually the xdebug was installed but I missed one configuration. The xdebug.ini file was with only the following line:
zend_extension=/usr/lib/php5/20121212/xdebug.so
I'd added the following lines:
xdebug.remote_enable=1
xdebug.remote_handler=dbgp
xdebug.remote_mode=req
xdebug.remote_host=127.0.0.1
xdebug.remote_port=9000
and it's working! Just reconfigured the eclipse debug and is working.