Description:
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hi, some object oriented architectures requires inner classes
i'm not good with english language so i write some examples:

in a library like PDO, now we can do some like this:

class Database
{
    public function prepareSql($sql){ return new Sql($sql)}
}

class Sql
{
    public function setValue($search, $replace){}
    public function executeQuery(){return new ExecutedQuery();}
}

class ExecutedQuery
{
    function fetch()
    function numRows()
    // etc
}

this api allows the developer to instantiate an ExecutedQuery with no Sql parameters escaping (class Sql)

so inner classes are useful to make visible classes in some trusted environment:

class Database
{
    public function prepareSql($sql){ return new Sql($sql)}

    class Sql
    {
        public function setValue($search, $replace){}
        public function executeQuery(){return new ExecutedQuery();}
        class ExecutedQuery
        {
            function fetch()
            function numRows()
            // etc
        }
    }
}

i've read a lot of rfc on php's wiki but no one talks about inner classes (useful like traits and others new work in progress features)

what do you think about this?