PHP SPL標準庫總共有6個接口，如下：
1.Countable
2.OuterIterator
3.RecursiveIterator
4.SeekableIterator
5.SplObserver
6.SplSubject
其中OuterIterator、RecursiveIterator、SeekableIterator都是繼承Iterator類的，下面會對每種接口作用和使用進行詳細說明。
Coutable接口：
實現Countable接口的對象可用于count()函數計數。
復制代碼代碼如下:
class Mycount implements Countable
{
public function count()
{
static $count = 0;
$count++;
return $count;
}
}
$count = new Mycount();
$count->count();
$count->count();
echo count($count); //3
echo count($count); //4
說明：
調用count()函數時，Mycount::count()方法被調用
count()函數的第二個參數將不會產生影響
OuterIterator接口：
自定義或修改迭代過程。
復制代碼代碼如下:
//IteratorIterator是OuterIterator的一個實現類
class MyOuterIterator extends IteratorIterator {
public function current()
{
return parent::current() . 'TEST';
}
}
foreach(new MyOuterIterator(new ArrayIterator(['b','a','c'])) as $key => $value) {
echo "$key->$value".PHP_EOL;
}
/*
結果：
0->bTEST
1->aTEST
2->cTEST
*/
在實際運用中，OuterIterator極其有用：
復制代碼代碼如下:
$db = new PDO('mysql:host=localhost;dbname=test', 'root', 'mckee');
$db->query('set names utf8');
$pdoStatement = $db->query('SELECT * FROM test1', PDO::FETCH_ASSOC);
$iterator = new IteratorIterator($pdoStatement);
$tenRecordArray = iterator_to_array($iterator);
print_r($tenRecordArray);
RecursiveIterator接口：
用于循環迭代多層結構的數據，RecursiveIterator另外提供了兩個方法：
RecursiveIterator::getChildren 獲取當前元素下子迭代器
RecursiveIterator::hasChildren 判斷當前元素下是否有迭代器
復制代碼代碼如下:
class MyRecursiveIterator implements RecursiveIterator
{
private $_data;
private $_position = 0;
public function __construct(array $data) {
$this->_data = $data;
}
public function valid() {
return isset($this->_data[$this->_position]);
}
public function hasChildren() {
return is_array($this->_data[$this->_position]);
}
public function next() {
$this->_position++;
}
public function current() {
return $this->_data[$this->_position];
}
public function getChildren() {
print_r($this->_data[$this->_position]);
}
public function rewind() {
$this->_position = 0;
}
public function key() {
return $this->_position;
}
}
$arr = array(0, 1=> array(10, 20), 2, 3 => array(1, 2));
$mri = new MyRecursiveIterator($arr);
foreach ($mri as $c => $v) {
if ($mri->hasChildren()) {
echo "$c has children: " .PHP_EOL;
$mri->getChildren();
} else {
echo "$v" .PHP_EOL;
}
}
/*
結果：
0
1 has children:
Array
(
[0] => 10
[1] => 20
)
2
3 has children:
Array
(
[0] => 1
[1] => 2
)
*/
SeekableIterator接口：
通過seek()方法實現可搜索的迭代器，用于搜索某個位置下的元素。
復制代碼代碼如下:
class MySeekableIterator implements SeekableIterator {
private $position = 0;
private $array = array(
"first element" ,
"second element" ,
"third element" ,
"fourth element"
);
public function seek ( $position ) {
if (!isset( $this -> array [ $position ])) {
throw new OutOfBoundsException ( "invalid seek position ( $position )" );
}
$this -> position = $position ;
}
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 ();
}
/*
結果：
first element
third element
second element
invalid seek position ( 10 )
*/
SplObserver和SplSubject接口:
SplObserver和SplSubject接口用來實現觀察者設計模式，觀察者設計模式是指當一個類的狀態發生變化時，依賴它的對象都會收到通知并更新。使用場景非常廣泛，比如說當一個事件發生后，需要更新多個邏輯操作，傳統方式是在事件添加后編寫邏輯，這種代碼耦合并難以維護，觀察者模式可實現低耦合的通知和更新機制。
看看SplObserver和SplSubject的接口結構：
復制代碼代碼如下:
//SplSubject結構 被觀察的對象
interface SplSubject{
public function attach(SplObserver $observer); //添加觀察者
public function detach(SplObserver $observer); //剔除觀察者
public function notify(); //通知觀察者
}
//SplObserver結構 代表觀察者
interface SplObserver{
public function update(SplSubject $subject); //更新操作
}
看下面一個實現觀察者的例子：
復制代碼代碼如下:
class Subject implements SplSubject
{
private $observers = array();
public function attach(SplObserver $observer)
{
$this->observers[] = $observer;
}
public function detach(SplObserver $observer)
{
if($index = array_search($observer, $this->observers, true)) {
unset($this->observers[$index]);
}
}
public function notify()
{
foreach($this->observers as $observer) {
$observer->update($this);
}
}
}
class Observer1 implements SplObserver
{
public function update(SplSubject $subject)
{
echo "邏輯1代碼".PHP_EOL;
}
}
class Observer2 implements SplObserver
{
public function update(SplSubject $subject)
{
echo "邏輯2代碼".PHP_EOL;
}
}
$subject = new Subject();
$subject->attach(new Observer1());
$subject->attach(new Observer2());
$subject->notify();
/*
結果：
邏輯1代碼
邏輯2代碼
*/
