The text editor nano manages syntax highlighting through .nanorc files. Say, we have files with the ending .phpx, but would like PHP syntax highlighting.

$ sudo nano /usr/share/nano/php.nanorc

Change this line

syntax "php" "\.php[2345s~]?$"

to this regex:

syntax "php" "\.php[x2345s~]?$".

Alternativly, e.g. if you don’t have sudo rights for /usr/share/nano/php.nanorc, you can do the following

$cp /usr/share/nano/php.nanorc ~/.phpx.nanorc

Then enter the following line in ~/.nanorc:

include ~/.phpx.nanorc

Then, change the line as mentioned above and syntax „php“ into syntax „phpx“