RewriteEngine On

# speedie.site/blog.php/* -> speedie.site/blog/*
RewriteCond %{THE_REQUEST} /blog\.php/(.+)\sHTTP [NC]
RewriteRule ^ /blog/%1 [NE,L,R]

# speedie.site/blog/* -> speedie.site/blog.php/*
RewriteCond %{REQUEST_FILENAME} !-d
RewriteCond %{REQUEST_FILENAME} !-f
RewriteRule ^blog/(.+)$ /blog.php/$1 [L]

# .php extension
RewriteCond %{THE_REQUEST} /([^.]+)\.php [NC]
RewriteRule ^ /%1 [NC,L,R]

RewriteCond %{REQUEST_FILENAME}.php -f
RewriteRule ^ %{REQUEST_URI}.php [NC,L]

# 404
ErrorDocument 404 /php/404.php