Solution 1:

Try this code for hiding .php (will work both ways):

Options +FollowSymLinks -MultiViews
# Turn mod_rewrite on
RewriteEngine On
RewriteBase /

## don't touch /forum URIs
RewriteRule ^forums/ - [L,NC]

## hide .php extension snippet

# To externally redirect /dir/foo.php to /dir/foo
RewriteCond %{THE_REQUEST} ^[A-Z]{3,}\s([^.]+)\.php [NC]
RewriteRule ^ %1 [R,L]

# To internally forward /dir/foo to /dir/foo.php
RewriteCond %{REQUEST_FILENAME} !-d
RewriteCond %{REQUEST_FILENAME}.php -f
RewriteRule ^(.*?)/?$ $1.php [L]

Solution 2:

try this.

<IfModule mod_rewrite.c>
RewriteEngine on
RewriteCond %{SCRIPT_FILENAME} !-d
RewriteCond %{SCRIPT_FILENAME} !-f
RewriteRule ^(.*)$ $1.php [L,QSA]
</IfModule>

if this not work then your sever do not have mod_rewrite activated or support url rewriting.