Interfaces
PHP Manual

The SeekableIterator interface

Introduction

The Seekable iterator.

Interface synopsis

SeekableIterator extends Iterator
/* Methods */
public void SeekableIterator::seek(int $offset)
/* Inherited methods */
public mixed Iterator::current()
public mixed Iterator::key()
public void Iterator::next()
public void Iterator::rewind()
public bool Iterator::valid()

Examples

Example #1 Basic usage

This example demonstrates creating a custom SeekableIterator, seeking to a position and handling an invalid position. 

<?php
class MySeekableIterator implements SeekableIterator {

    private $position;

    private $array = array(
        "first element",
        "second element",
        "third element",
        "fourth element"
    );

    /* Method required for SeekableIterator interface */

    public function seek($position) {
      if (!isset($this->array[$position])) {
          throw new OutOfBoundsException("invalid seek position ($position)");
      }

      $this->position = $position;
    }

    /* Methods required for Iterator interface */
    
    public function rewind() {
        $this->position = 0;
    }

    public function current() {
        return $this->array[$this->position];
    }

    public function key() {
        return $this->position;
    }

    public function next() {
        ++$this->position;
    }

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

try {

    $it = new MySeekableIterator;
    echo $it->current(), "\n";
    
    $it->seek(2);
    echo $it->current(), "\n";
    
    $it->seek(1);
    echo $it->current(), "\n";
    
    $it->seek(10);
    
} catch (OutOfBoundsException $e) {
    echo $e->getMessage();
}
?>

The above example will output something similar to:

first element
third element
second element
invalid seek position (10)
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