At this point, let's say I have a class like so:
class Sentence {
__construct($content) {
$this->content = $content;
}
public function grab_word($num) {
$words = explode(" ", $this->content);
return $words[$num+1];
}
}
So the interface given would allow me to create a new Sentence, and then I could call the grab_word() class method to fetch a word in the sentence:
$sentence = new Sentence("Lorem ipsum dolor sit amet");
echo $sentence->grab_word(2);
However, what I'd like to do is add another chained class method, giving me the ability to capitalize this word.
$sentence->grab_word(2); # -> ipsum
$sentence->grab_word(2)->caps(); # -> IPSUM
Clearly, this won't work because chained methods require object inheritance. If I were to create caps() and chain that function - it would return an error due to the return not being the inherited Sentence object.
To sum it up, my question is how to I achieve the ability to chain these methods optionally, but still return a non-object whenever needed (like in my output example).
Broadly speaking, what you're asking is not possible. Why don't you just always return the object you sometimes need to chain method calls onto? Just return new Word($words[ ... ]) and you'll be in a better position.
Now, when I say "broadly speaking", there are things you can do to make it possible to call different methods, that may live in different classes. You can make use of __call() to implement something similar to ruby's mixins, though really quite inferior. __call() will simply look at the method name that was invoked, then iterate a list of possible targets and see if they respond to that method, before delegating the invocation to that object (or raising an exception).
PS: This question hasn't got anything to do with inheritance. Method chaining requires returning an object, not just implementing an inheritance hierarchy. Of course, you may return $this, where that makes sense, but usually you return another object.