The Iterator interface

(PHP 5, PHP 7, PHP 8)

Introduction

Interface for external iterators or objects that can be iterated themselves internally.

Interface synopsis

interface Iterator extends Traversable {
/* Methods */
public current(): mixed
public key(): mixed
public next(): void
public rewind(): void
public valid(): bool
}

Predefined iterators

PHP already provides a number of iterators for many day to day tasks. See SPL iterators for a list.

Examples

Example #1 Basic usage

This example demonstrates in which order methods are called when using foreach with an iterator.

<?php
class myIterator implements Iterator {
    private 
$position 0;
    private 
$array = array(
        
"firstelement",
        
"secondelement",
        
"lastelement",
    );  

    public function 
__construct() {
        
$this->position 0;
    }

    public function 
rewind(): void {
        
var_dump(__METHOD__);
        
$this->position 0;
    }

    
#[\ReturnTypeWillChange]
    
public function current() {
        
var_dump(__METHOD__);
        return 
$this->array[$this->position];
    }

    
#[\ReturnTypeWillChange]
    
public function key() {
        
var_dump(__METHOD__);
        return 
$this->position;
    }

    public function 
next(): void {
        
var_dump(__METHOD__);
        ++
$this->position;
    }

    public function 
valid(): bool {
        
var_dump(__METHOD__);
        return isset(
$this->array[$this->position]);
    }
}

$it = new myIterator;

foreach(
$it as $key => $value) {
    
var_dump($key$value);
    echo 
"\n";
}
?>

The above example will output something similar to:

string(18) "myIterator::rewind"
string(17) "myIterator::valid"
string(19) "myIterator::current"
string(15) "myIterator::key"
int(0)
string(12) "firstelement"

string(16) "myIterator::next"
string(17) "myIterator::valid"
string(19) "myIterator::current"
string(15) "myIterator::key"
int(1)
string(13) "secondelement"

string(16) "myIterator::next"
string(17) "myIterator::valid"
string(19) "myIterator::current"
string(15) "myIterator::key"
int(2)
string(11) "lastelement"

string(16) "myIterator::next"
string(17) "myIterator::valid"

See Also

See also object iteration.

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