RewriteEngine On

# Agar exact file exist karti hai (with .php), direct open
RewriteCond %{REQUEST_FILENAME}.php -f
RewriteRule ^(.+)$ $1.php [L]

# Agar folder nahi hai aur .php file bhi nahi hai to block
RewriteCond %{REQUEST_FILENAME} !-d
RewriteCond %{REQUEST_FILENAME}.php !-f
RewriteRule ^ - [R=404,L]