Look at the actions of PHP in the internal iteration

Let's look at how to implement a self-defined iterator and then begin to understand how the iterator works internally. Let's take a look at an official example:

<?
Phpclass Myiterator implements Iterator {    private $position = 0;    Private $array = Array (        "First_element",        "Second_element",        "Last_element",    );      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 = + $value) {echo ' output key value: ';    Var_dump ($key, $value);//echo $key;    echo "\ n";}

program execution output:

String "Myiterator::rewind" string (myiterator::valid) "Myiterator::current" string (15) " Myiterator::key "Output key value: Int (0) string (" First_element "string ()" Myiterator::next "string (" Myiterator::valid ") String ("Myiterator::current" string "Myiterator::key" Output key value: Int (1) string "Second_element" string (16) " Myiterator::next "string (myiterator::valid)" string "Myiterator::current" string ("Myiterator::key") Output key value: Int (2) string (last_element) "Myiterator::next" string (+) "Myiterator::valid"

The following methods are required inside a generic iterator:

• Iterator::current-return the current element returns
• Iterator::key-return the key of the current element returns the keys
• Iterator::next-move forward to next element moves to the next
• Iterator::rewind-rewind the Iterator to the first element again
• Iterator::valid-checks If position is valid check the validity of the current location

Assume that the content workflow of the iterator is not very clear. The ability to view the following iterator traversal of an array:

<?
php/*** @author [Email protected]*/class myiterator implements iterator{private $var = Array ();         Public function __construct ($array) {if (Is_array ($array)) {$this->var = $array;        }} Public Function rewind () {echo "rewind the first element \ n";     Reset ($this->var);         The public Function current () {$var = current ($this->var);         echo "current element: $var \ n";     return $var;         Public Function key () {$var = key ($this->var);         echo "Key of current element: $var \ n";     return $var;         Public function Next () {$var = next ($this->var);         echo "moves to the next element: $var \ n";     return $var;         Public Function Valid () {$var = $this->current ()!== false;         echo "Check validity: {$var}\n";     return $var; }} $values = Array (n/a), $it = new Myiterator ($values), foreach ($it as $k + = $v) {print "At this time key-value pair-key $k: Value $v \ n ";}

Program Execution Results:

today, is it very clear?

Copyright notice: This article blog original articles, blogs, without consent, may not be reproduced.

Look at the actions of PHP in the internal iteration