Edit $HOME/.nanorc to contain the following:
include /usr/share/nano/java.nanorc
include /usr/share/nano/man.nanorc
include /usr/share/nano/nanorc.nanorc
include /usr/share/nano/python.nanorc
include /usr/share/nano/sh.nanorc
include /usr/share/nano/html.nanorc
include /usr/share/nano/perl.nanorc
include /usr/share/nano/php.nanorc
CentOS 7 uses a much older version of nano than the one that presently ships on most distributions. The php.nanorc on newer The following should appear in /usr/share/nano/php.nanorc on CentOS7 to allow syntax highlighting for php:
## Syntax highlighting for PHP
syntax "php" "\.(php[23457s~]?|phtml|ctp)$"
# PHP markings.
color brightgreen "()"
# Function names.
color white "\