Expose "length" filter, make it work with Countable objects

[rundef]

I needed to count the number of elements in an array ...
I saw that this feature has been talked about in issue #33

I wasn't sure if I should have created a new filter |count for objects only ... Tell me what you think!

[fprochazka]

imho it should be something like

public static function length($s)
{
    if (is_array($s)) {
        return count($s);
    } elseif ($s instanceof \Traversable) {
        return iterator_count($s);
    } else {
        return strlen(utf8_decode($s)): // fastest way
    }
}

[dg]

if (is_array($val) || $val instanceof \Countable)

[xificurk]

A test would be nice ;-)

[rundef]

Thanks for the quick feedback :)

[dg]

Thanks, merged

[hrach]

this (may) mutate the iterator, imo it's best to let decide the programmer.

iterator_count() is not guaranteed to retain the current position of the iterator.
http://php.net/iterator_count