This answer is for XAMPP on Ubuntu.
The manual for installation and download is on (site official)
http://www.apachefriends.org/it/xampp-linux.html
After to start XAMPP simply call this command:
sudo /opt/lampp/lampp start
You should now see something like this on your screen:
Starting XAMPP 1.8.1...
LAMPP: Starting Apache...
LAMPP: Starting MySQL...
LAMPP started.
If you have this 
Starting XAMPP for Linux 1.8.1...                                                             
XAMPP: Another web server daemon is already running.                                          
XAMPP: Another MySQL daemon is already running.                                               
XAMPP: Starting ProFTPD...                                                                    
XAMPP for Linux started
.  The solution is 
sudo /etc/init.d/apache2 stop
sudo /etc/init.d/mysql stop
And the restast with sudo //opt/lampp/lampp restart
You to fix most of the security weaknesses simply call the following command:
/opt/lampp/lampp security
After the change this file 
sudo kate //opt/lampp/etc/extra/httpd-xampp.conf
Find and replace on 
    #
# New XAMPP security concept
#
<LocationMatch "^/(?i:(?:xampp|security|licenses|phpmyadmin|webalizer|server-status|server-info))">
    Order deny,allow
    Deny from all
    Allow from ::1 127.0.0.0/8 
    Allow from all
    #\
    #   fc00::/7 10.0.0.0/8 172.16.0.0/12 192.168.0.0/16 \
    #   fe80::/10 169.254.0.0/16
    ErrorDocument 403 /error/XAMPP_FORBIDDEN.html.var
</LocationMatch>