简单明了的回答。

function flatten_array(array $array)
{
    return iterator_to_array(
         new \RecursiveIteratorIterator(new \RecursiveArrayIterator($array)));
}

用法:

$array = [
    'name' => 'Allen Linatoc',
    'profile' => [
        'age' => 21,
        'favourite_games' => [ 'Call of Duty', 'Titanfall', 'Far Cry' ]
    ]
];

print_r( flatten_array($array) );

输出(在PsySH):

Array
(
    [name] => Allen Linatoc
    [age] => 21
    [0] => Call of Duty
    [1] => Titanfall
    [2] => Far Cry
)

现在就看你怎么处理钥匙了。干杯

编辑(2017-03-01)

引用Nigel Alderton的担忧/问题:

澄清一下，这保留了键(甚至是数字键)，因此具有相同键的值将丢失。例如数组美元= [a, [' b ', ' c ']]成为数组([0]= > b, c[1] = >)。“a”丢失了，因为“b”也有一个键值为0

引用Svish的回答:

只需将false作为第二个参数($use_keys)添加到iterator_to_array调用中

因为这里的代码看起来很可怕。下面是一个将多维数组转换为html格式兼容语法的函数，但它更容易阅读。

/**
 * Flattens a multi demensional array into a one dimensional
 * to be compatible with hidden html fields.
 *
 * @param array $array
 *  Array in the form:
 *  array(
 *    'a' => array(
 *      'b' => '1'
 *    )
 *  )
 *
 * @return array
 *  Array in the form:
 *  array(
 *    'a[b]' => 1,
 *  )
 */
function flatten_array($array) {
  // Continue until $array is a one-dimensional array.
  $continue = TRUE;
  while ($continue) {
    $continue = FALSE;

    // Walk through top and second level of $array and move 
    // all values in the second level up one level.
    foreach ($array as $key => $value) {
      if (is_array($value)) {
        // Second level found, therefore continue.
        $continue = TRUE;

        // Move each value a level up.
        foreach ($value as $child_key => $child_value) {
          $array[$key . '[' . $child_key . ']'] = $child_value;
        }

        // Remove second level array from top level.
        unset($array[$key]);
      }
    }
  }

  return $array;
}

如果你想保留中间键:

function flattenArray(array &$result, $value, string $key = "")
{
    if (!is_array($value)) {
        $result[$key] = $value;
        return $result;
    }
    foreach ($value as $subKey => $subArray) {
        $newKey = $key !== "" ? $key . "_" . $subKey : $subKey;
        flattenArray($result, $subArray, $newKey);
    }
    return $result;
}

$nestedArray = [
    "name" => "John",
    "pets" => [
        ["id" => 1, "name" => "snooop"],
        ["id" => 2, "name" => "medor"],
    ],
    "job" => ["title" => "developper"],
];

$intermediateResult = [];
$flattened = flattenArray($intermediateResult, $nestedArray);
var_dump($flattened);

这将输出:

array(6) {
["name"]=>
  string(4) "John"
        ["pets_0_id"]=>
  int(1)
  ["pets_0_name"]=>
  string(6) "snooop"
        ["pets_1_id"]=>
  int(2)
  ["pets_1_name"]=>
  string(5) "medor"
        ["job_title"]=>
  string(10) "developper"
}

看到https://ideone.com/KXLtzZ stdout

如果你想保住你的钥匙，那就是解决办法。

function flatten(array $array) {
    $return = array();
    array_walk_recursive($array, function($value, $key) use (&$return) { $return[$key] = $value; });
    return $return;
}

不幸的是，它只输出最后的嵌套数组，没有中间键。对于下面的例子:

$array = array(
    'sweet' => array(
        'a' => 'apple',
        'b' => 'banana'),
    'sour' => 'lemon'); 
print_r(flatten($fruits));

输出是:

Array
(
    [a] => apple
    [b] => banana
    [sour] => lemon
)

我相信这是最干净的解决方案，不使用任何突变或不熟悉的类。

<?php

function flatten($array)
{
    return array_reduce($array, function($acc, $item){
        return array_merge($acc, is_array($item) ? flatten($item) : [$item]);
    }, []);
}


// usage
$array = [1, 2, [3, 4], [5, [6, 7]], 8, 9, 10];
print_r(flatten($array));

如果你有一个对象数组，想用一个节点把它压平，只需要使用这个函数:

function objectArray_flatten($array,$childField) {
    $result = array();
    foreach ($array as $node)
    {
        $result[] = $node;
        if(isset($node->$childField))
        {
            $result = array_merge(
                $result, 
                objectArray_flatten($node->$childField,$childField)
            );
            unset($node->$childField);
        }

    }
    return $result;
}