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The Traversable interface

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.

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
6 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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