Combining iterators with AppendIterator

- As its name suggest, the Append Iterator class…appends iterators one right after another.…So, they run consecutively.…To demonstrates its use,…I've opened append.php, which confined in the…Chapter 4 folder of the exercise files.…This file contains the definition of…Author Filer, that's the custom class…that extends filter iterator that we created in Chapter 3.…Then on line 18, the data in course is .XML…is loaded as simple XML.…

We'll use the Author Filter class…to select courses by a couple of authors.…So, we first need to add simple XML iterator…and the second argument to simple XML load file.…That enables us to use it as an iterator.…Then, we'll create a couple of iterators…to select courses by me and Jon Peck.…So, Powers new Author Filter…repass it a simple XML iterator courses,…and then the second argument is the name of the author,…that's me David Powers.…

Then, another one for Jon Peck, new author filter.…the same courses iterator, and then Jon's name.…We could iterator over these independently,…but let's use Append Iterators,…