php 如何检查变量是否是数组？...或类似数组的东西

How to check if variable is array?... or something array-like

提问by Voitcus

I want to use a foreachloop with a variable, but this variable can be many different types, NULLfor example.

我想使用一个foreach带有变量的循环，但NULL例如，这个变量可以是许多不同的类型。

So before foreachI test it:

所以在foreach我测试之前：

if(is_array($var)){
  foreach($var as ...

But I realized that it can also be a class that implements Iteratorinterface. Maybe I am blind but how to check whether the class implements interface? Is there something like is_afunction or inheritsoperator? I found class_implements, I can use it, but maybe there is something simpler?

但是我意识到它也可以是一个实现Iterator接口的类。也许我瞎了，但是如何检查类是否实现了接口？有is_a函数或inherits运算符之类的东西吗？我发现class_implements，我可以使用它，但也许有更简单的东西？

And second, more important, I suppose this function exist, would be enough to check if the variable is_arrayor "implements Iteratorinterface" or should I test for something more?

其次，更重要的是，我认为这个函数存在，足以检查变量is_array或“实现Iterator接口”是否应该测试更多内容？

采纳答案by Shoe

If you are using foreachinside a function and you are expecting an array or a Traversableobject you can type hint that function with:

如果您foreach在函数内部使用并且您需要一个数组或一个Traversable对象，您可以输入提示该函数：

function myFunction(array $a)
function myFunction(Traversable)

If you are not using foreachinside a function or you are expecting both you can simply use this constructto check if you can iterate over the variable:

如果您不在foreach函数内部使用，或者您期望两者都使用，则可以简单地使用此构造来检查是否可以迭代变量：

if (is_array($a) or ($a instanceof Traversable))

回答by hakre

foreachcan handle arrays and objects. You can check this with:

foreach可以处理数组和对象。您可以通过以下方式检查：

$can_foreach = is_array($var) || is_object($var);
if ($can_foreach) {
    foreach ($var as ...
}

You don't need to specifically check for Traversableas others have hinted it in their answers, because all objects - like all arrays - are traversable in PHP.

您不需要Traversable像其他人在他们的答案中暗示的那样专门检查，因为所有对象 - 就像所有数组一样 - 在 PHP 中都是可遍历的。

More technically:

从技术上讲：

foreachworks with all kinds of traversables, i.e. with arrays, with plain objects (where the accessible properties are traversed) and Traversableobjects (or rather objects that define the internal get_iteratorhandler).

foreach适用于各种可遍历对象，即数组、普通对象（遍历可访问属性的地方）和Traversable对象（或者更确切地说是定义内部get_iterator处理程序的对象）。

(source)

（来源）

Simply said in common PHP programming, whenever a variable is

简单地说，在普通的 PHP 编程中，每当一个变量

• an array
• an object

• 数组
• 一个东西

and is not

并且不是

• NULL
• a resource
• a scalar

• 空值
• 一种资源
• 标量

you can use foreachon it.

你可以使用foreach它。

回答by Baba

You can check instance of Traversablewith a simple function. This would work for all this of Iteratorbecause Iterator extends Traversable

您可以Traversable使用一个简单的函数检查实例。这对所有这些都有效，Iterator因为Iterator extends Traversable

function canLoop($mixed) {
    return is_array($mixed) || $mixed instanceof Traversable ? true : false;
}

回答by Alexey

<?php
$var = new ArrayIterator();

var_dump(is_array($var), ($var instanceof ArrayIterator));

returns bool(false)or bool(true)

返回bool(false)或bool(true)

回答by Eduardo Cuomo

Functions

职能

<?php

/**
 * Is Array?
 * @param mixed $x
 * @return bool
 */
function isArray($x) : bool {
  return !isAssociative($x);
}

/**
 * Is Associative Array?
 * @param mixed $x
 * @return bool
 */
function isAssociative($x) : bool {
  if (!is_array($array)) {
    return false;
  }
  $i = count($array);
  while ($i > 0) {
    if (!isset($array[--$i])) {
      return true;
    }
  }
  return false;
}

Example

例子

<?php

$arr = [ 'foo', 'bar' ];
$obj = [ 'foo' => 'bar' ];

var_dump(isAssociative($arr));
# bool(false)

var_dump(isAssociative($obj));
# bool(true)

var_dump(isArray($obj));
# bool(false)

var_dump(isArray($arr));
# bool(true)

回答by faintsignal

Since PHP 7.1 there is a pseudo-type iterablefor exactly this purpose. Type-hinting iterableaccepts any array as well as any implementation of the Traversableinterface. PHP 7.1 also introduced the function is_iterable(). For older versions, see other answers here for accomplishing the equivalent type enforcement without the newer built-in features.

从 PHP 7.1 开始，有一个伪类型就是iterable为了这个目的。类型提示iterable接受任何数组以及Traversable接口的任何实现。PHP 7.1 也引入了该功能is_iterable()。对于旧版本，请参阅此处的其他答案，以在没有较新的内置功能的情况下完成等效的类型强制。

Fair play: As BlackHole pointed out, this question appears to be a duplicate of Iterable objects and array type hinting?and his or her answergoes into further detail than mine.

公平竞赛：正如 BlackHole 所指出的，这个问题似乎是Iterable 对象和数组类型提示的重复？和他或她的答案进入更详细的比我的。