An iterable is any value that can be looped through with a foreach() loop. Introduced in PHP 7.1, the iterable pseudo-type can be used for function arguments and return values.
The iterable keyword can be used as a data type for function arguments or as a return type for functions.
Use iterable as a type for a function argument to accept any value that can be looped through with a foreach() loop.
| <?php function printIterable(iterable $myIterable) { foreach($myIterable as $item) { echo $item; } } $arr = [“a”, “b”, “c”]; printIterable($arr); ?> |
Return an iterable
| <?php function getIterable():iterable { return [“a”, “b”, “c”]; } $myIterable = getIterable(); foreach($myIterable as $item) { echo $item; } ?> |
Arrays: All arrays in PHP are iterables, meaning they can be used as arguments for functions that accept iterables.
Iterators: Any object implementing the Iterator interface can serve as an argument for functions requiring an iterable. An iterator maintains a list of items with a pointer to one of the elements and provides methods for traversal.
A valid iterator must implement these methods:
current(): Returns the current element pointed to by the iterator, which can be of any data type.key(): Returns the key associated with the current element. The key must be an integer, float, boolean, or string.next(): Moves the pointer to the next element in the list.rewind(): Resets the pointer to the first element in the list.valid(): Returns false if the pointer is not pointing to any element (e.g., after next() is called at the end), and true otherwise.Implement the Iterator interface and use it as an iterable.
| <?php // Create an Iterator class MyIterator implements Iterator { private $items = []; private $pointer = 0; public function __construct($items) { // array_values() makes sure that the keys are numbers $this->items = array_values($items); } public function current() { return $this->items[$this->pointer]; } public function key() { return $this->pointer; } public function next() { $this->pointer++; } public function rewind() { $this->pointer = 0; } public function valid() { // count() indicates how many items are in the list return $this->pointer < count($this->items); } } // A function that uses iterables function printIterable(iterable $myIterable) { foreach($myIterable as $item) { echo $item; } } // Use the iterator as an iterable $iterator = new MyIterator([“a”, “b”, “c”]); printIterable($iterator); ?> |