IteratorAggregate interface in PHP - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is the purpose of the IteratorAggregate interface in PHP?

The <code>IteratorAggregate</code> interface allows a class to specify an external iterator by implementing the <code>getIterator()</code> method, which returns an instance of <code>Traversable</code>. This lets the class be used in <code>foreach</code> loops.

beginner

Which method must a class implement when it uses the <code>IteratorAggregate</code> interface?

A class must implement the <code>getIterator()</code> method, which returns an object that implements <code>Traversable</code>, usually an <code>Iterator</code>.

intermediate

How does IteratorAggregate differ from Iterator in PHP?

IteratorAggregate requires only one method getIterator() that returns an iterator, while Iterator requires multiple methods (current(), next(), key(), valid(), rewind()) to control iteration directly.

beginner

What type of object should <code>getIterator()</code> return in a class implementing <code>IteratorAggregate</code>?

The getIterator() method should return an object that implements Traversable, typically an instance of Iterator or ArrayIterator.

intermediate

Why would you use IteratorAggregate instead of Iterator?

Using <code>IteratorAggregate</code> lets you separate the iteration logic from the class itself by returning an external iterator. This can simplify the class and reuse existing iterator classes.

Which method is required by the IteratorAggregate interface?

A getIterator()

B current()

C next()

D rewind()

The IteratorAggregate interface requires the getIterator() method only.

What should getIterator() return?

A An object implementing Traversable

B An array

C A string

D A boolean

getIterator() must return an object that implements Traversable.

Which interface requires implementing current(), next(), and rewind() methods?

A Countable

B IteratorAggregate

C ArrayAccess

D Iterator

Iterator requires these methods to control iteration.

Why use IteratorAggregate instead of Iterator?

A To avoid using foreach loops

B To separate iteration logic by returning an external iterator

C To implement multiple iterators at once

D To make the class non-iterable

IteratorAggregate allows returning an external iterator, separating iteration logic.

Which of these is a valid iterator class to return from getIterator()?

A Exception

B DateTime

C ArrayIterator

D PDO

ArrayIterator implements Iterator and can be returned from getIterator().

Explain how the IteratorAggregate interface works and when you would use it.

Think about how iteration is handled outside the class.

Describe the difference between IteratorAggregate and Iterator interfaces in PHP.

Focus on how iteration methods are implemented.