The CachingIterator class

(PHP 5, PHP 7, PHP 8)


This object supports cached iteration over another iterator.

Sommario della classe

class CachingIterator extends IteratorIterator implements ArrayAccess, Countable, Stringable {
/* Costanti */
public const int CALL_TOSTRING;
public const int CATCH_GET_CHILD;
public const int TOSTRING_USE_KEY;
public const int TOSTRING_USE_CURRENT;
public const int TOSTRING_USE_INNER;
public const int FULL_CACHE;
/* Metodi */
public __construct(Iterator $iterator, int $flags = CachingIterator::CALL_TOSTRING)
public count(): int
public current(): mixed
public getCache(): array
public getFlags(): int
public hasNext(): bool
public key(): scalar
public next(): void
public offsetExists(string $key): bool
public offsetGet(string $key): mixed
public offsetSet(string $key, mixed $value): void
public offsetUnset(string $key): void
public rewind(): void
public setFlags(int $flags): void
public __toString(): string
public valid(): bool
/* Metodi ereditati */
public IteratorIterator::next(): void

Costanti predefinite


Convert every element to string.


Don't throw exception in accessing children.


Use key for conversion to string.


Use current for conversion to string.


Use inner for conversion to string.


Cache all read data.

Log delle modifiche

Versione Descrizione
8.0.0 CachingIterator implements Stringable now.

Indice dei contenuti

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User Contributed Notes 4 notes

ahmad dot mayahi at gmail dot com
6 years ago
//This snippet will print out all the cached elements (foreach) .

$cache  = new CachingIterator(new ArrayIterator(range(1,100)), CachingIterator::FULL_CACHE);

foreach (
$cache as $c) {


ahmad dot mayahi at gmail dot com
2 years ago
The only difference between CachingIterator and other Iterators such as ArrayIterator is the hasNext() method.

Since the data will be loaded into the memory, the CachingIterator is able to check whether the given iterator has a next element.

Let's demonstrate this by an example:

= new CachingIterator(new ArrayIterator(['C', 'C++', 'C#', 'PHP', 'Python', 'Go', 'Ruby']));

foreach (
$iterator as $item) {
    if (
$iterator->hasNext()) {
$item.', ';
    } else {
'and '.$item;

// C, C++, C#, PHP, Python, Go, and Ruby

In this example I check whether the iterator has a next value, if so, I append a comma otherwise "and" will be appended to the last element.
xedin dot unknown at gmail dot com
2 years ago
Apparently, the `FULL_CACHE` flag automatically cancels the default flag `CALL_TOSTRING`. This is evident when one of the values cannot be converted to string: with the default `CALL_TOSTRING` flag, it would throw an error; without that flag, or with the `FULL_CACHE` flag, it does not.
jerome at chaman dot ca
2 years ago
"cached iteration over another iterator" means this iterator is always one step behind the inner iterator. In other words, the "first" iteration will yield null:


= new CachingIterator( new ArrayIterator( [ 'a', 'b', 'c']  ) );

$cit->current() ); // null
echo $cit->getInnerIterator()->current() ); // "a"

// we start with a "next" since the "first" item is null
$cit->current(), '<br>';

iterating this way gives us an access, ahead, to the future item (aka current item of the inner iterator)
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