This maybe trivial but I think it is worth sharing anyway
Consider using LIMIT/OFFSET in a function where as parameter you have to specify values for both.
In the following function both limit and offset parameters are integers. This will cause an error when you want to pass ALL (for LIMIT ALL) as argument.

PostgreSQL function:

create or replace function sp_category_getlist
	(plimit integer,poffset integer) returns setof category as
$$
	select *
	from
		category
        order by
		caption
	limit
		$1 offset $2
$$
language sql;

Fortunately PostgreSQL accepts NULL function arguments which in this case is treated as ALL

Example in PHP:

/* sp_filesystem_category_getlist */
public function sp_filesystem_category_getlist
	($puserid,$plimit=null,$poffset='0')
{
	$args = array($plimit,$poffset);
	$sql = "select * from sp_filesystem_category_getlist($1,$2)";
	$result=$this->query($sql,$args);
	return pg_fetch_all($result);
}