我比较数组的键值和数组的array_values()结果的键值之间的差异，数组始终是一个具有整数下标的数组。如果键是相同的，它就不是一个关联数组。

function isHash($array) {
    if (!is_array($array)) return false;
    $diff = array_diff_assoc($array, array_values($array));
    return (empty($diff)) ? false : true;
}

仅仅检查数组是否有非整数键(而不是数组是否按顺序索引或零索引):

function has_string_keys(array $array) {
  return count(array_filter(array_keys($array), 'is_string')) > 0;
}

如果至少有一个字符串键，$array将被视为一个关联数组。

实际上，我发现自己遇到了类似的情况，试图获取一个数组并将其解析为XML。XML元素名称不能以数字开头——我发现的代码片段不能正确处理带有数字索引的数组。

我的具体情况如下

上面@null (http://stackoverflow .com/a/173589/293332)提供的答案实际上非常接近。我对它被否决感到沮丧:那些不懂正则表达式的人过着非常令人沮丧的生活。

总之，根据他的回答，我得出了以下结论:

/** 
 * Checks if an array is associative by utilizing REGEX against the keys
 * @param   $arr    <array> Reference to the array to be checked
 * @return  boolean
 */     
private function    isAssociativeArray( &$arr ) {
    return  (bool)( preg_match( '/\D/', implode( array_keys( $arr ) ) ) );
}

更多细节请参见PCRE转义序列和PCRE语法页面。

我的特殊情况

这是我正在处理的一个示例数组:

Case A

return  array(
    "GetInventorySummary"  => array(
        "Filters"  => array( 
            "Filter"  => array(
                array(
                    "FilterType"  => "Shape",
                    "FilterValue"  => "W",
                ),
                array(
                    "FilterType"  => "Dimensions",
                    "FilterValue"  => "8 x 10",
                ),
                array(
                    "FilterType"  => "Grade",
                    "FilterValue"  => "A992",
                ),
            ),
        ),
        "SummaryField"  => "Length",
    ),
);

问题是过滤器键是可变的。例如:

Case B

return  array(
    "GetInventorySummary"  => array(
        "Filters"  => array( 
            "Filter"  => array(
                "foo"   =>  "bar",
                "bar"   =>  "foo",
            ),
        ),
        "SummaryField"  => "Length",
    ),
);

为什么我需要协会。检查数组

如果我要转换的数组像情况A一样，我想要返回的是:

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<GetInventorySummary>
    <Filters>
        <Filter>
            <FilterType>Shape</FilterType>
            <FilterValue>W</FilterValue>
        </Filter>
        <Filter>
            <FilterType>Dimensions</FilterType>
            <FilterValue>8 x 10</FilterValue>
        </Filter>
        <Filter>
            <FilterType>Grade</FilterType>
             <FilterValue>A992</FilterValue>
        </Filter>
    </Filters>
    <SummaryField>Length</SummaryField>
</GetInventorySummary>

．.． 然而，如果我要转换的数组像Case B一样，我想要返回的是:

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<GetInventorySummary>
    <Filters>
        <Filter>
            <foo>bar</foo>
            <bar>foo</bar>
        </Filter>
    </Filters>
    <SummaryField>Length</SummaryField>
</GetInventorySummary>

PHP 8.1增加了一个内置函数来确定数组是否是具有这些语义的列表。函数是array_is_list:

$list = ["a", "b", "c"];

array_is_list($list); // true

$notAList = [1 => "a", 2 => "b", 3 => "c"];

array_is_list($notAList); // false

$alsoNotAList = ["a" => "a", "b" => "b", "c" => "c"];

array_is_list($alsoNotAList); // false

参考

答案已经给出了，但关于表现的虚假信息太多了。 我写了这个小的基准测试脚本，它显示foreach方法是最快的。

免责声明:以下方法是从其他答案复制粘贴的

<?php

function method_1(Array &$arr) {
    return $arr === array_values($arr);
}

function method_2(Array &$arr) {
    for (reset($arr), $i = 0; key($arr) !== $i++; next($arr));
    return is_null(key($arr));
}

function method_3(Array &$arr) {
    return array_keys($arr) === range(0, count($arr) - 1);
}

function method_4(Array &$arr) {
    $idx = 0;
    foreach( $arr as $key => $val ){
        if( $key !== $idx )
            return FALSE;
        $idx++;
    }
    return TRUE;
}




function benchmark(Array $methods, Array &$target){    
    foreach($methods as $method){
        $start = microtime(true);
        for ($i = 0; $i < 1000; $i++)
            $dummy = call_user_func($method, $target);

        $end = microtime(true);
        echo "Time taken with $method = ".round(($end-$start)*1000.0,3)."ms\n";
    }
}



$targets = [
    'Huge array' => range(0, 30000),
    'Small array' => range(0, 1000),
];
$methods = [
    'method_1',
    'method_2',
    'method_3',
    'method_4',
];
foreach($targets as $targetName => $target){
    echo "==== Benchmark using $targetName ====\n";
    benchmark($methods, $target);
    echo "\n";
}

结果:

==== Benchmark using Huge array ====
Time taken with method_1 = 5504.632ms
Time taken with method_2 = 4509.445ms
Time taken with method_3 = 8614.883ms
Time taken with method_4 = 2720.934ms

==== Benchmark using Small array ====
Time taken with method_1 = 77.159ms
Time taken with method_2 = 130.03ms
Time taken with method_3 = 160.866ms
Time taken with method_4 = 69.946ms

一种廉价而肮脏的方法是这样检查:

isset($myArray[count($myArray) - 1])

.．.如果你的数组是这样的，你可能会得到一个假阳性:

$myArray = array("1" => "apple", "b" => "banana");

一个更彻底的方法可能是检查钥匙:

function arrayIsAssociative($myArray) {
    foreach (array_keys($myArray) as $ind => $key) {
        if (!is_numeric($key) || (isset($myArray[$ind + 1]) && $myArray[$ind + 1] != $key + 1)) {
            return true;
        }
    }
    return false;
}
// this will only return true if all the keys are numeric AND sequential, which
// is what you get when you define an array like this:
// array("a", "b", "c", "d", "e");

or

function arrayIsAssociative($myArray) {
    $l = count($myArray);
    for ($i = 0; $i < $l, ++$i) {
        if (!isset($myArray[$i])) return true;
    }
    return false;
}
// this will return a false positive on an array like this:
$x = array(1 => "b", 0 => "a", 2 => "c", 4 => "e", 3 => "d");