Why can't I access Xampp's phpmyadmin on localhost? Access is forbidden.

The solution can be found here. Summary follows:

Edit /opt/lampp/etc/extra/httpd-xampp.conf.

Add the line Require all granted to the bottom of the <Directory "/opt/lampp/phpmyadmin"> block as follows:

<Directory "/opt/lampp/phpmyadmin">
  AllowOverride AuthConfig Limit
  Order allow,deny
  Allow from all
  Require all granted
</Directory>

I solved this by creating a new virtual host for phpmyadmin

For windows systems:

Append the following to C:/xampp/apache/conf/httpd.conf:

NameVirtualHost phpmyadmin.local

<VirtualHost phpmyadmin.local>
  ServerName phpmyadmin.local
  DocumentRoot "C:/xampp/htdocs/phpmyadmin"
  <Directory "C:/xampp/htdocs/phpmyadmin">
    AllowOverride All
    Allow from All
  </Directory>
</VirtualHost>

Change the DocumentRoot/Directory to the path where you have installed your version of phpmyadmin.

Open the C:\Windows\System32\drivers\etc\hosts file in a text editor and add the following line:

127.0.0.1     phpmyadmin.local

then save the hosts file and restart xampp.