PHP編程--疊代器（乾貨，愛拿不拿）技术頭條網

2018-02-11 00:22:00 冰雪緣

* PHP迭代器講義

* ArrayIterator迭代器多用於對數組的迭代，他能完成一般遍歷方法無法完場的

* 操作！

* ------------------------------------------------------------*/

echo '

';#構建數組
$array = [
'first' => 'first value',
'second' => 'second value',
'third' => 'third value',
'fourth' => 'fourth value',
'fifth' => 'fifth value',
];
/*
* foreach ($array as $key => $value){
* echo '鍵名：' . $key . '|' . '鍵值' . $value . '
';
* }
*
* 結果：
* 鍵名：first|鍵值first value
* 鍵名：second|鍵值second value
* 鍵名：third|鍵值third value
* 鍵名：fourth|鍵值fourth value
* 鍵名：fifth|鍵值fifth value
*
* 通過for循環呢？
* for ($i = 0; i < count($array); i++{
* 遍歷代碼
* }
* */
#實例化 ArrayIterator，把接力棒交給$arrayObj
$arrayObj = new ArrayObject($array);
/*
* print_r($arrayObj);
*
ArrayIterator Object
(
[storage:ArrayIterator:private] => Array
(
[first] => first value
[second] => second value
[third] => third value
[fourth] => fourth value
[fifth] => fifth value
)
)
* */
#獲取迭代器
$iterator = $arrayObj -> getIterator();
/*
* print_r($iterator);
*
ArrayIterator Object
(
[storage:ArrayIterator:private] => ArrayObject Object
(
[storage:ArrayObject:private] => Array
(
[first] => first value
[second] => second value
[third] => third value
[fourth] => fourth value
[fifth] => fifth value
)
)
)
* */
/*
* foreach ($iterator as $key => $value){
echo '鍵名：' . $key . '|' . '鍵值' . $value . '
';
}
結果：
鍵名：first|鍵值first value
鍵名：second|鍵值second value
鍵名：third|鍵值third value
鍵名：fourth|鍵值fourth value
鍵名：fifth|鍵值fifth value
這時候，不能用for循環了。
試試while循環
*/
/*
* 指向第一個節點，也是說雙向數據鏈表的bottom位置
$iterator->rewind();
while ($iterator -> valid()){
echo $iterator -> key() . '|' . $iterator -> current() . '
';
$iterator -> next();
}
運行結果：
first|first value
second|second value
third|third value
fourth|fourth value
fifth|fifth value
*/
$iterator->rewind();
#跳過first鍵名，從second鍵名開始，用seek方法。
$iterator->seek(1);
while ($iterator -> valid()){
echo $iterator -> key() . '|' . $iterator -> current() . '
';
$iterator -> next();
}