The Traversable interface

(PHP 5 >= 5.0.0)

Introduction

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.

Note:

Internal (built-in) classes that implement this interface can be used in a foreach construct and do not need to implement IteratorAggregate or Iterator.

Note:

This is an internal engine interface which cannot be implemented in PHP scripts. Either IteratorAggregate or Iterator must be used instead. When implementing an interface which extends Traversable, make sure to list IteratorAggregate or Iterator before its name in the implements clause.

Interface synopsis

Traversable {
}

This interface has no methods, its only purpose is to be the base interface for all traversable classes.

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User Contributed Notes 2 notes

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35
kevinpeno at gmail dot com
4 years ago
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
?>
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-30
mathdegiovani at gmail dot com
8 months ago
Note that instanceof Traversable does not work for stdclass objects, so if you are this check (as @kevinpeno) to decide whether you can iterate, it will fail for direct instances.

In particular:

<?php

$obj
= new stdclass();
$obj->prop = 'hello';
var_dump($obj instanceof Traversable);
//outputs bool(false)
?>

My own solution is to check whether the object also descends from stdclass, but that also fails to catch some objects that are iterable.
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