I have the following regular expression for Friendly URL:
RewriteRule ^categoria/([a-z0-9-]+)/([a-z0-9-]+)/([a-z0-9-]+)/?$ categoria.php?idc=$1&nome=$2&pg=$3 [NC]
I would like to leave the 3 parameter, pg, optional, have or have not. The way I'm using it is mandatory to provide the 3 parameter.
Did you try this?
RewriteRule ^categoria\/([a-z0-9-]+)\/([a-z0-9-]+)(\/([a-z0-9-]+))?\/?$ categoria.php?idc=$1&nome=$2&pg=$4 [NC]
So you put one group inside the other and make the parent parameter optional by including the slash. In the response variable, you just skip the parent parameter ($ 3) until you find the child parameter ($ 4).