By default, the .php extension will show in a web browsers address bar. For example, if you've a page named About.php, the address bar will show www.example.com/About.php.

Ensure the rewrite module is enabled. If rewrite_module is in the list of modules of the following command, then the rewrite_module is enabled.

[root@server1 ~]# httpd -M
. . .
rewrite_module (shared)

In the /etc/httpd/conf/httpd.conf file, inside of <Directory /var/www>, ensure AllowOverride is set to All.

<Directory /var/www>
. . .
AllowOverride All

Restart HTTPD, and ensure HTTPD is active and running.

[root@server1 ~]# systemctl restart httpd
[root@server1 ~]# systemctl status httpd

Use the apachectl configtest command can be used to verify the configuaration of HTTPD is OK.

[root@server1 ~]# apachectl configtest
. . .
Syntax OK

Create the .htaccess file.

[root@server1 ~]# touch /var/www/html/.htaccess

Edit the .htaccess file, and add the following.

RewriteEngine On
RewriteRule ^about$ about.php [NC]

Now, .php will no longer be displayed.