Using SPL recursive iterators

The Standard PHP Library SPL has many built-in iterators for recursion purposes. We can use them as per our need, without taking the pain of implementing them from scratch. Here is the list of iterators and their functionality:

• RecursiveArrayIterator: This recursive iterator allows iterating over any type of array or objects and modifying the key or values or unsetting them. It also allows iterating over the current iterator entry.

• RecursiveCallbackFilterIterator: If we are looking forward to applying a callback recursively to any array or objects, this iterator can be very helpful.

• RecursiveDirectoryIterator: This iterator allows iterating any directory or filing systems. It makes the directory listing very easy. For example, we can rewrite the directory listing program we wrote in this chapter easily using this iterator:

$path = realpath...