RecursiveFilterIterator

RecursiveFilterIterator is a class in PHP that allows for filtering of iterators in a recursive manner. It extends the FilterIterator class and enables the filtering of nested iterators. This means that not only the current level of an iterator is filtered, but also any iterators contained within it.

The primary purpose of RecursiveFilterIterator is to traverse and filter a tree-like structure of data represented by nested iterators. It takes another iterator as its first argument, which is the iterator to be filtered. Subsequent arguments are used to define the filtering logic.

When iterating over a RecursiveFilterIterator, only elements that pass the filter condition at all levels of recursion are yielded. This is achieved by overriding the accept() method of the parent FilterIterator class. The accept() method is responsible for determining whether the current element should be included in the iteration.

RecursiveFilterIterator is particularly useful when dealing with complex, hierarchical data structures like file system directories, XML documents, or abstract syntax trees, where you need to selectively extract information based on certain criteria across multiple levels of nesting. It simplifies the process of filtering such structures compared to manual recursive traversal.