Php-SPL库中的迭代器类详解(转)

SPL提供了多个迭代器类，分别提供了迭代访问、过滤数据、缓存结果、控制分页等功能。，因为php总是在不断壮大，我尽可能列出SPL中所有的迭代类。下面其中一些迭代器类是需要php5.4，另外一些如SearhIteratoer类在最新的php版本中已经去除

1.ArrayIteratoer

从PHP数组创建一个迭代器，当其和IteratorAggregate类一起使用时，免去了直接实现Iterator接口的方法的工作。

<示例>

 $b = array(
     'name'=> 'mengzhi',
     'age' => '12',
     'city'=> 'shanghai'
 );
 $a = new ArrayIterator($b);
 $a->append(array(
                 'home' => 'china',
                 'work' => 'developer'
            ));
 $c = $a->getArrayCopy();
 print_r($a);
 print_r($c);
 
 /**output
 ArrayIterator Object
 (
     [storage:ArrayIterator:private] => Array
     (
     [name] => mengzhi
             [age] => 12
             [city] => shanghai
             [0] => Array
     (
     [home] => china
                     [work] => developer
                 )
 
         )
 
 )
 Array
     (
     [name] => mengzhi
     [age] => 12
     [city] => shanghai
     [0] => Array
     (
     [home] => china
             [work] => developer
         )
 
 )
 **/

2. LimitIterator

返回给定数量的结果以及从集合中取出结果的起始索引点：

<示例>

 // Create an iterator to be limited
 $fruits = new ArrayIterator(array(
                                  'apple',
                                  'banana',
                                  'cherry',
                                  'damson',
                                  'elderberry'
                             ));
 // Loop over first three fruits only
 foreach (new LimitIterator($fruits, 0, 3) as $fruit) {
     var_dump($fruit);
 }
 echo "\n";
 // Loop from third fruit until the end
 // Note: offset starts from zero for apple
 foreach (new LimitIterator($fruits, 2) as $fruit) {
     print_r($fruit);
 }
 
 /**output
 string(5) "apple"
 string(6) "banana"
 string(6) "cherry"
 
 cherrydamsonelderberry
  */

3. AppendIterator

按顺序迭代访问几个不同的迭代器。例如，希望在一次循环中迭代访问两个或者更多的组合。这个迭代器的append方法类似于array_merge()函数来合并数组。

 $array_a = new ArrayIterator(array('a', 'b', 'c'));
 $array_b = new ArrayIterator(array('d', 'e', 'f'));
 $iterator = new AppendIterator;
 $iterator->append($array_a);
 $iterator->append($array_b);
 foreach ($iterator as $current) {
     echo $current."\n";
 }
 /**output
 a
 b
 c
 d
 e
 f
  */

4. FilterIterator

基于OuterIterator接口，用于过滤数据，返回符合条件的元素。必须实现一个抽象方法accept()，此方法必须为迭代器的当前项返回true或false

 class UserFilter extends FilterIterator
 {
     private $userFilter;
 
     public function __construct(Iterator $iterator, $filter)
     {
         parent::__construct($iterator);
         $this->userFilter = $filter;
     }
 
     public function accept()
     {
         $user = $this->getInnerIterator()->current();
         if (strcasecmp($user['name'], $this->userFilter) == 0) {
             return false;
         }
         return true;
     }
 }
 
 $array = array(
     array(
         'name' => 'Jonathan',
         'id'   => '5'
     ),
     array(
         'name' => 'Abdul',
         'id'   => '22'
     )
 );
 $object = new ArrayObject($array);
 //去除掉名为abdul的人员
 $iterator = new UserFilter($object->getIterator(), 'abdul');
 foreach ($iterator as $result) {
     echo $result['name'];
 }
 
 /**output
 Jonathan
 **/

5. RegexIterator

继承FilterIterator，支持使用正则表达式模式匹配和修改迭代器中的元素。经常用于将字符串匹配。

 $a = new ArrayIterator(array('test1', 'test2', 'test3'));
 $i = new RegexIterator($a, '/^(test)(\d+)/', RegexIterator::REPLACE);
 $i->replacement = '$2:$1';
 print_r(iterator_to_array($i));
 
 /**output
 Array
 (
     [0] => 1:test
     [1] => 2:test
     [2] => 3:test
 )
  **/

6. IteratorIterator

一种通用类型的迭代器，所有实现了Traversable接口的类都可以被它迭代访问。

7. CachingIterator

用来执行提前读取一个元素的迭代操作，例如可以用于确定当前元素是否为最后一个元素。

 $array = array('koala', 'kangaroo', 'wombat', 'wallaby', 'emu', 'kiwi', 'kookaburra', 'platypus');
 try {
     $object = new CachingIterator(new ArrayIterator($array));
     foreach ($object as $value) {
         echo $value;
         if ($object->hasNext()) {
             echo ',';
         }
     }
 }
 catch (Exception $e) {
     echo $e->getMessage();
 }
 /**output
 koala,kangaroo,wombat,wallaby,emu,kiwi,kookaburra,platypus
  **/

8. SeekableIterator

用于创建非顺序访问的迭代器，允许跳转到迭代器中的任何一点上。

 $array = array("apple", "banana", "cherry", "damson", "elderberry");
 $iterator = new ArrayIterator($array);
 $iterator->seek(3);
 echo $iterator->current();
 /**output
 damson
  **/

9. NoRewindIterator

用于不能多次迭代的集合，适用于在迭代过程中执行一次性操作。

 $fruit = array('apple', 'banana', 'cranberry');
 $arr = new ArrayObject($fruit);
 $it = new NoRewindIterator($arr->getIterator());
 echo "Fruit A:\n";
 foreach ($it as $item) {
     echo $item . "\n";
 }
 
 echo "Fruit B:\n";
 foreach ($it as $item) {
     echo $item . "\n";
 }
 /**output
 Fruit A:
 apple
 banana
 cranberry
 Fruit B:
  **/

10. EmptyIterator

一种占位符形式的迭代器，不执行任何操作。当要实现某个抽象类的方法并且这个方法需要返回一个迭代器时，可以使用这种迭代器。

11. InfiniteIterator

用于持续地访问数据，当迭代到最后一个元素时，会再次从第一个元素开始迭代访问。

 $arrayit = new ArrayIterator(array('cat', 'dog'));
 $infinite = new InfiniteIterator($arrayit);
 $limit = new LimitIterator($infinite, 0, 7);
 foreach ($limit as $value) {
     echo "$value\n";
 }
 /**output
 cat
 dog
 cat
 dog
 cat
 dog
 cat
  **/

12. RecursiveArrayIterator

创建一个用于递归形式数组结构的迭代器，类似于多维数组.它为许多更复杂的迭代器提供了所需的操作，如RecursiveTreeIterator和RecursiveIteratorIterator迭代器。

$fruits = array("a" => "lemon", "b" => "orange", array("a" => "apple", "p" => "pear"));
$iterator = new RecursiveArrayIterator($fruits);
while ($iterator->valid()) {
    //检查是否含有子节点
    if ($iterator->hasChildren()) {
        //输出所以字节点
        foreach ($iterator->getChildren() as $key => $value) {
            echo $key . ' : ' . $value . "\n";
        }
    } else {
        echo "No children.\n";
    }
    $iterator->next();
}
 
/**output
No children.
No children.
a : apple
p : pear
 **/

13. RecursiveIteratorIterator

将一个树形结构的迭代器展开为一维结构。

 $fruits = array("a" => "lemon", "b" => "orange", array("a" => "apple", "p" => "pear"));
 $arrayiter = new RecursiveArrayIterator($fruits);
 $iteriter = new RecursiveIteratorIterator($arrayiter);
 foreach ($iteriter as $key => $value) {
     $d = $iteriter->getDepth();
     echo "depth=$d k=$key v=$value\n";
 }
 
 /**output
 depth=0 k=a v=lemon
 depth=0 k=b v=orange
 depth=1 k=a v=apple
 depth=1 k=p v=pear
  **/

14. RecursiveTreeIterator

以可视在方式显示一个树形结构。

 $hey = array("a" => "lemon", "b" => "orange", array("a" => "apple", "p" => "pear"));
 $awesome = new RecursiveTreeIterator(
     new RecursiveArrayIterator($hey),
     null, null, RecursiveIteratorIterator::LEAVES_ONLY
 );
 foreach ($awesome as $line)
     echo $line . PHP_EOL;
 
 /**output
 |-lemon
 |-orange
     |-apple
     \-pear
  **/

15. ParentIterator

是一个扩展的FilterIterator迭代器，它可以过滤掉来自于RecursiveIterator迭代器的非父元素，只找出子节点的键值。通俗来说，就是去枝留叶。

 $hey = array("a" => "lemon", "b" => "orange", array("a" => "apple", "p" => "pear"));
 $arrayIterator = new RecursiveArrayIterator($hey);
 $it = new ParentIterator($arrayIterator);
 print_r(iterator_to_array($it));
 /**output
 Array
     (
     [0] => Array
     (
         [a] => apple
         [p] => pear
     )
 )
  **/

16. RecursiveFilterIterator

是FilterIterator迭代器的递归形式，也要求实现抽象的accept()方法，但在这个方法中应该使用$this->getInnerIterator()方法访问当前正在迭代的迭代器。

 class TestsOnlyFilter extends RecursiveFilterIterator
 {
     public function accept()
     {
         // 找出含有“叶”的元素
         return $this->hasChildren() || (mb_strpos($this->current(), "叶") !== FALSE);
     }
 }
 
 $array = array("叶1", array("李2", "叶3", "叶4"), "叶5");
 $iterator = new RecursiveArrayIterator($array);
 $filter = new TestsOnlyFilter($iterator);
 $filter = new RecursiveIteratorIterator($filter);
 print_r(iterator_to_array($filter));
 /**output
 Array
 (
     [0] => 叶1
     [1] => 叶3
     [2] => 叶5
 )
 **/

17. RecursiveRegexIterator

是RegexIterator迭代器的递归形式，只接受RecursiveIterator迭代器作为迭代对象。

 $rArrayIterator = new RecursiveArrayIterator(array('叶1', array('tet3', '叶4', '叶5')));
 $rRegexIterator = new RecursiveRegexIterator($rArrayIterator, '/^叶/',
     RecursiveRegexIterator::ALL_MATCHES);
 
 foreach ($rRegexIterator as $key1 => $value1) {
     if ($rRegexIterator->hasChildren()) {
         // print all children
         echo "Children: ";
         foreach ($rRegexIterator->getChildren() as $key => $value) {
             echo $value . " ";
         }
         echo "\n";
     } else {
         echo "No children\n";
     }
 }
 /**output
 No children
 Children: 叶4 叶5
  **/

18. RecursiveCachingIterator

在RecursiveIterator迭代器上执行提前读取一个元素的递归操作。

19. CallbackFilterIterator(PHP5.4)

同时执行过滤和回调操作，在找到一个匹配的元素之后会调用回调函数。

 $hey = array( "李1", "叶2", "叶3", "叶4", "叶5", "叶6",);
 $arrayIterator = new RecursiveArrayIterator($hey);
 function isYe($current)
 {
     return mb_strpos($current,'叶') !== false;
 }
 
 $rs = new CallbackFilterIterator($arrayIterator, 'isYe');
 print_r(iterator_to_array($rs));
 
 /**output
 Array
 (
     [0] => 叶2
     [1] => 叶3
     [2] => 叶4
     [3] => 叶5
     [4] => 叶6
 )
  **/

20. DirectoryIterator

目录文件遍历器

方    法	描    述
DirectoryIterator::getSize	得到文件大小
DirectoryIterator::getType	得到文件类型
DirectoryIterator::isDir	如果当前项是一个目录，返回true
DirectoryIterator::isDot	如果当前项是.或..，返回true
DirectoryIterator::isExecutable	如果文件可执行，返回true
DirectoryIterator::isFile	如果文件是一个常规文件，返回true
DirectoryIterator::isLink	如果文件是一个符号链接，返回true
DirectoryIterator::isReadable	如果文件可读，返回true
DirectoryIterator::isWritable	如果文件可写，返回true
DirectoryIterator::key	返回当前目录项
DirectoryIterator::next	移动到下一项
DirectoryIterator::rewind	将目录指针返回到开始位置
DirectoryIterator::valid	检查目录中是否包含更多项

 $it = new DirectoryIterator("../");
 foreach ($it as $file) {
     //用isDot ()方法分别过滤掉“.”和“..”目录
     if (!$it->isDot()) {
         echo $file . "\n";
     }
 }

21. RecursiveDirectoryIterator

递归目录文件遍历器，可实现列出所有目录层次结构，而不是只操作一个目录。

方    法	描    述
RecursiveDirectoryIterator::getChildren	如果这是一个目录，为当前项返回一个迭代器
RecursiveDirectoryIterator::hasChildren	返回当前项是否是一个目录而不是.或..
RecursiveDirectoryIterator::key	返回当前目录项的路径和文件名
RecursiveDirectoryIterator::next	移动到下一项
RecursiveDirectoryIterator::rewind	将目录指针返回到开始位置
RecursiveIteratorIterator::current	访问当前元素值
RecursiveIteratorIterator::getDepth	得到递归迭代的当前深度
RecursiveIteratorIterator::getSubIterator	得到当前活动子迭代器
RecursiveIteratorIterator::key	访问当前键
RecursiveIteratorIterator::next	前移到下一个元素
RecursiveIteratorIterator::rewind	将迭代器返回到顶级内层迭代器的第一个元素
RecursiveIteratorIterator::valid	检查当前位置是否合法

 //列出指定目录中所有文件
 $path = realpath('../');
 $objects = new RecursiveIteratorIterator(new RecursiveDirectoryIterator($path), RecursiveIteratorIterator::SELF_FIRST);
 foreach ($objects as $name => $object) {
     echo "$name\n";
 }

22. FilesystemIterator

是DirectoryIterator的遍历器

 $it = new FilesystemIterator('../');
 foreach ($it as $fileinfo) {
     echo $fileinfo->getFilename() . "\n";
 }

23. GlobIterator

带匹配模式的文件遍历器

//找出../目录中.php扩展名的文件
$iterator = new GlobIterator('./*.php');
if (!$iterator->count()) {
    echo '无php文件';
} else {
    $n = 0;
    printf("总计 %d 个php文件\r\n", $iterator->count());
    foreach ($iterator as $item) {
        printf("[%d] %s\r\n", ++$n, $iterator->key());
    }
}
/**output
总计 23 个php文件
[1] .\1.php
[2] .\11.php
[3] .\12.php
[4] .\13.php
[5] .\14.php
[6] .\15.php
[7] .\16.php
[8] .\17.php
[9] .\19.php
[10] .\2.php
[11] .\20.php
[12] .\21.php
[13] .\22.php
[14] .\23.php
[15] .\24.php
[16] .\25.php
[17] .\26.php
[18] .\3.php
[19] .\4.php
[20] .\5.php
[21] .\7.php
[22] .\8.php
[23] .\9.php
 **/

24. MultipleIterator

用于迭代器的连接器，具体看示例

 $person_id = new ArrayIterator(array('001', '002', '003'));
 $person_name = new ArrayIterator(array('张三', '李四', '王五'));
 $person_age = new ArrayIterator(array(22, 23, 11));
 $mit = new MultipleIterator(MultipleIterator::MIT_KEYS_ASSOC);
 $mit->attachIterator($person_id, "ID");
 $mit->attachIterator($person_name, "NAME");
 $mit->attachIterator($person_age, "AGE");
 echo "连接的迭代器个数:".$mit->countIterators() . "\n"; //
 foreach ($mit as $person) {
     print_r($person);
 }
 /**output
 Array
 (
     [ID] => 001
     [NAME] => 张三
     [AGE] => 22
 )
 Array
 (
     [ID] => 002
     [NAME] => 李四
     [AGE] => 23
 )
 Array
 (
     [ID] => 003
     [NAME] => 王五
     [AGE] => 11
 )
  **/

25. RecursiveCallbackFilterIterator(PHP5.4)

在RecursiveIterator迭代器上进行递归操作，同时执行过滤和回调操作，在找到一个匹配的元素之后会调用回调函数。

 function doesntStartWithLetterT($current)
 {
     $rs = $current->getFileName();
     return $rs[0] !== 'T';
 }
 
 $rdi = new RecursiveDirectoryIterator(__DIR__);
 $files = new RecursiveCallbackFilterIterator($rdi, 'doesntStartWithLetterT');
 foreach (new RecursiveIteratorIterator($files) as $file) {
     echo $file->getPathname() . PHP_EOL;
 }

26. SimpleXMLIterator

XMl文档访问迭代器，可实现访问xml中所有节点

 $xml = <<<XML
 <books>
     <book>
         <title>PHP Basics</title>
         <author>Jim Smith</author>
     </book>
     <book>XML basics</book>
 </books>
 XML;
 // SimpleXML转换为数组
 function sxiToArray($sxi)
 {
     $a = array();
     for ($sxi->rewind(); $sxi->valid(); $sxi->next()) {
         if (!array_key_exists($sxi->key(), $a)) {
             $a[$sxi->key()] = array();
         }
         if ($sxi->hasChildren()) {
             $a[$sxi->key()][] = sxiToArray($sxi->current());
         } else {
             $a[$sxi->key()][] = strval($sxi->current());
         }
     }
     return $a;
 }
 
 $xmlIterator = new SimpleXMLIterator($xml);
 $rs = sxiToArray($xmlIterator);
 print_r($rs);
 /**output
 Array
 (
     [book] => Array
         (
             [0] => Array
                 (
                     [title] => Array
                         (
                             [0] => PHP Basics
                         )
 
                     [author] => Array
                         (
                             [0] => Jim Smith
                         )
 
                 )
 
             [1] => XML basics
         )
 
 )
  **/