Php-SPL库中的迭代器类详解

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:".$mit->countIterators() . "\n"; //3
foreach ($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
        )

)
 **/

********************************************

* 作者：叶文涛 

* 标题：Php-SPL库中的迭代器类详解

* 参考：

*  php手册http://php.net/manual/en/spl.iterators.php

*《PHP高级程序设计：模式、框架和测试》 Kevin McArthur 著 汪泳 等译

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