function is_array_assoc($foo) {
    if (is_array($foo)) {
        return (count(array_filter(array_keys($foo), 'is_string')) > 0);
    }
    return false;
}

或者你可以用这个:

Arr::isAssoc($array)

它将检查数组是否包含任何非数字键或:

Arr:isAssoc($array, true)

检查数组是否严格顺序(包含自动生成的int键0到n-1)

使用这个库。

除非PHP有这样的内置功能，否则您无法在小于O(n)的时间内完成—枚举所有键并检查整数类型。事实上，你还想确保没有漏洞，所以你的算法可能是这样的:

for i in 0 to len(your_array):
    if not defined(your-array[i]):
        # this is not an array array, it's an associative array :)

但为什么要麻烦呢?只需假设数组是您所期望的类型。如果不是，它就会在你面前爆炸——这就是动态编程!测试你的代码，一切都会很好……

我认为标量数组的定义因应用程序而异。也就是说，一些应用程序将需要更严格的定义标量数组，而一些应用程序将需要更宽松的定义。

下面我将介绍3种不同严格程度的方法。

<?php
/**
 * Since PHP stores all arrays as associative internally, there is no proper
 * definition of a scalar array.
 * 
 * As such, developers are likely to have varying definitions of scalar array,
 * based on their application needs.
 * 
 * In this file, I present 3 increasingly strict methods of determining if an
 * array is scalar.
 * 
 * @author David Farrell <DavidPFarrell@gmail.com>
 */

/**
 * isArrayWithOnlyIntKeys defines a scalar array as containing
 * only integer keys.
 * 
 * If you are explicitly setting integer keys on an array, you
 * may need this function to determine scalar-ness.
 * 
 * @param array $a
 * @return boolean
 */ 
function isArrayWithOnlyIntKeys(array $a)
{
    if (!is_array($a))
        return false;
    foreach ($a as $k => $v)
        if (!is_int($k))
            return false;
    return true;
}

/**
 * isArrayWithOnlyAscendingIntKeys defines a scalar array as
 * containing only integer keys in ascending (but not necessarily
 * sequential) order.
 * 
 * If you are performing pushes, pops, and unsets on your array,
 * you may need this function to determine scalar-ness.
 * 
 * @param array $a
 * @return boolean
 */ 
function isArrayWithOnlyAscendingIntKeys(array $a)
{
    if (!is_array($a))
        return false;
    $prev = null;
    foreach ($a as $k => $v)
    {
        if (!is_int($k) || (null !== $prev && $k <= $prev))
            return false;
        $prev = $k;
    }
    return true;
}

/**
 * isArrayWithOnlyZeroBasedSequentialIntKeys defines a scalar array
 * as containing only integer keys in sequential, ascending order,
 * starting from 0.
 * 
 * If you are only performing operations on your array that are
 * guaranteed to either maintain consistent key values, or that
 * re-base the keys for consistency, then you can use this function.
 * 
 * @param array $a
 * @return boolean
 */
function isArrayWithOnlyZeroBasedSequentialIntKeys(array $a)
{
    if (!is_array($a))
        return false;
    $i = 0;
    foreach ($a as $k => $v)
        if ($i++ !== $k)
            return false;
    return true;
}

这是解决方案吗?

  public static function isArrayAssociative(array $array) {
      reset($array);
      return !is_int(key($array));
  }

需要注意的是，数组光标被重置了，但我想说的是，这个函数可能在数组被遍历或使用之前就被使用了。

只是补充我的意见，我认为它应该是相当有效的基于@nonsensei的基准，以及清晰易读:

function is_associative(array $array): bool
{
    foreach ($array as $key => $value)
    {
        if (!is_string($key)) return false;
    }
    return true;
}