While you cannot implement this interface, you can use it in your checks to determine if something is usable in for each. Here is what I use if I'm expecting something that must be iterable via foreach.
<?php
if( !is_array( $items ) && !$items instanceof Traversable )
//Throw exception here
?>
The Traversable interface
(PHP 5, PHP 7, PHP 8)
Introduzione
Interface to detect if a class is traversable using foreach.
Abstract base interface that cannot be implemented alone. Instead, it must be implemented by either IteratorAggregate or Iterator.
Sommario dell'interfaccia
interface Traversable {
}This interface has no methods, its only purpose is to be the base interface for all traversable classes.
Log delle modifiche
| Versione | Descrizione |
|---|---|
| 7.4.0 | The Traversable interface can now be implemented by abstract classes. Extending classes must implement Iterator or IteratorAggregate. |
Note
Nota:
Internal (built-in) classes that implement this interface can be used in a foreach construct and do not need to implement IteratorAggregate or Iterator.
Nota:
Prior to PHP 7.4.0, this internal engine interface couldn't be implemented in PHP scripts. Either IteratorAggregate or Iterator must be used instead.
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User Contributed Notes 5 notes
kevinpeno at gmail dot com ¶
14 years ago
cobaltbluedw ¶
8 years ago
NOTE: While objects and arrays can be traversed by foreach, they do NOT implement "Traversable", so you CANNOT check for foreach compatibility using an instanceof check.
Example:
$myarray = array('one', 'two', 'three');
$myobj = (object)$myarray;
if ( !($myarray instanceof \Traversable) ) {
print "myarray is NOT Traversable";
}
if ( !($myobj instanceof \Traversable) ) {
print "myobj is NOT Traversable";
}
foreach ($myarray as $value) {
print $value;
}
foreach ($myobj as $value) {
print $value;
}
Output:
myarray is NOT Traversable
myobj is NOT Traversable
one
two
three
one
two
three
douglas at reith dot com dot au ¶
7 years ago
The PHP7 iterable pseudo type will match both Traversable and array. Great for return type-hinting so that you do not have to expose your Domain to Infrastructure code, e.g. instead of a Repository returning a Cursor, it can return hint 'iterable':
<?php
UserRepository::findUsers(): iterable
?>
Link: http://php.net/manual/en/migration71.new-features.php#migration71.new-features.iterable-pseudo-type
Also, instead of:
<?php
if( !is_array( $items ) && !$items instanceof Traversable )
//Throw exception here
?>
You can now do with the is_iterable() method:
<?php
if ( !is_iterable( $items ))
//Throw exception here
?>
Link: http://php.net/manual/en/function.is-iterable.php
ajf at ajf dot me ¶
9 years ago
Note that all objects can be iterated over with foreach anyway and it'll go over each property. This just describes whether or not the class implements an iterator, i.e. has custom behaviour.
alan dot bem at gmail dot com ¶
6 years ago
Actually you can use `Traversable` within your php scripts - you can use it to enforce iterability on user-land objects.
<?php
interface Stream implements \Traversable {}
class InMemoryStream implements IteratorAggregate, Stream
{
public function getIterator() {}
}
$stream = new InMemoryStream();
?>
In case you'd forgot about implementing `IteratorAggregate` or `Iterator` interfaces, fatal error will be raised when instantiating objects in question.
<?php
interface Stream implements \Traversable {}
class InMemoryStream implements Stream {}
$stream = new InMemoryStream(); // Fatal error: Class InMemoryStream must implement interface Traversable as part of either Iterator or IteratorAggregate in Unknown on line 0
?>
