php—Iterator interface

You can iterate internally with your own external iterator or interface of a class.

Interface summary

Iterator extends Traversable {
    /* 方法 */
    abstract public mixed current ( void )
    abstract public scalar key ( void )
    abstract public void next ( void )
    abstract public void rewind ( void )
    abstract public boolean valid ( void )
}

Predefined iterators

PHP already provides some iterators for daily tasks, such as SPL iterators.

Example

Example #1 Basic usage

This example shows the calling sequence of iterator methods when using foreach.

<?php
    class myIterator implements Iterator {
        private $position = 0;
        private $array = array(
            "firstelement",
            "secondelement",
            "lastelement",
        );
        public function __construct() {
            $this->position = 0;
        }
        function rewind() {
            var_dump(__METHOD__);
            $this->position = 0;
        }
        function current() {
            var_dump(__METHOD__);
            return $this->array[$this->position];
        }
        function key() {
            var_dump(__METHOD__);
            return $this->position;
        }
        function next() {
            var_dump(__METHOD__);
            ++$this->position;
        }
        function valid() {
            var_dump(__METHOD__);
            return isset($this->array[$this->position]);
        }
    }
    $it = new myIterator;
    foreach($it as $key => $value) {
        var_dump($key, $value);
        echo "\n";
    }
?>

The output of the above routine is 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"

Method list

Iterator::current — Returns the current element

Iterator::key — Returns the key of the current element

Iterator::next — Moves forward to the next An element

Iterator::rewind — Returns the first element of the iterator

Iterator::valid — Checks whether the current position is valid