如何在PHP的foreach循环中重复特定的迭代？

Posted 2021-05-05

由于php中没有迭代器，因此在不获取数组长度的情况下循环遍历数组的唯一方法是使用foreach循环。

假设我有以下循环：

foreach ($testing_array as $testing_entry) {
    $result = my_testing_api_call($testing_entry);
    if ($result == 'server dead')
        break;
    else if ($result == 'done') {
        // do something to handle success code
        continue;
    }
    else {
        sleep(5);
        // I want to retry my_testing_api_call with current $testing entry, but don't know what to write
    }
}

一种方法是使用for循环。

for ( $i=0; $i < count($testing_array); $i++ ) {
    $result = my_testing_api_call($testing_entry[$i]);
    if ($result == 'server dead')
        break;
    else if ($result == 'done') {
        // do something to handle success code
        continue;
    }
    else {
        sleep(5);
        $i--; //so it will repeat the current iteration.
    }
}

问题是$testing_array最初并不使用数字作为索引，所以我必须做一些数据按摩才能使用for循环。有没有办法在foreach循环中重复特定的迭代？

答案

也许一段时间会对你有用。

未经测试的代码：

foreach ($testing_array as $testing_entry) {
    do {
        $result = my_testing_api_call($testing_entry);
        if ($result == 'server dead') {
            break 2;  // break both loops
        } elseif ($result == 'done') {
            // do something to handle success code
        } else {
            sleep(5);
            // I want to retry my_testing_api_call with current $testing entry, but don't know what to write
        }
    } while ($result !== 'done');
}

---

或者是一个循环结构，它在迭代时破坏输入数组。

未经测试的代码：

$result = '';
while ($testing_array && $result !== 'server dead') {
    $result = my_testing_api_call(current($testing_array));
    if ($result == 'done') {
        // do something to handle success code
        array_shift($testing_array);
    } elseif ($result !== 'server dead') {
        sleep(5); // I want to retry my_testing_api_call with current $testing entry, but don't know what to write
    }
}

---

或者你可以使用你的for循环，通过$test_array与array_values()索引，如果你不需要你的// do something中的键。

$testing_array = array_values($testing_array);
for ($i=0, $count=count($testing_array); $i < $count; ++$i) {
    $result = my_testing_api_call($testing_entry[$i]);
    if ($result == 'server dead') {
        break;
    } else if ($result == 'done') {
        // do something to handle success code
    } else {
        sleep(5);
        --$i; //so it will repeat the current iteration.
    }
}

如果你确实需要按键向下脚本，但是你想使用for，你可以存储一个索引的键数组，这将允许你使用$i访问键并保持数据同步。

---

My final suggestion:

使用while (key($testing_array) !== null) {...}移动指针而不破坏元素。

代码：（Demo）

$array1 = [
    "one" => 1,
    "two" => 2,
    "three" => 3,
    "four" => 4
];

while (key($array1)!==null) {  // check if the internal pointer points beyond the end of the elements list or the array is empty
    $current = current($array1);
    $key = key($array1);
    echo "$key => $current
";         // display current key value pair
    if ($current < 3) {                // an arbitrary condition
        echo "	";
        $array1[$key] = ++$current;    // increment the current value
    } else {                           // current value is satisfactory
        echo "	(advance pointer)
";
        next($array1);                 // move pointer
    }
}

输出：

one => 1
    one => 2
    one => 3
    (advance pointer)
two => 2
    two => 3
    (advance pointer)
three => 3
    (advance pointer)
four => 4
    (advance pointer)

另一答案

你试图在循环中处理两个不同的东西，这使得编写干净的控制流很困难。您可以将重试逻辑与结果处理分开：

function call_api_with_retry($entry) {
  do {
    if (is_defined($result)) sleep(5);
    $result = my_testing_api_call($entry);
  } while ($result != 'done' && $result != 'server dead');
  return $result;
}

foreach ($testing_array as $testing_entry) {
    $result = call_api_with_retry($testing_entry);
    if ($result == 'server dead')
        break;
    else if ($result == 'done') {
        // do something to handle success code
        continue;
    }
}

（可能存在语法错误，自编写PHP代码以来已经有一段时间了）