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));

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;
}

这是我的解决方案，使用了一个参考:

function arrayFlatten($array_in, &$array_out){

    if(is_array($array_in)){
        foreach ($array_in as $element){
               arrayFlatten($element, $array_out);
        }
    }
    else{
        $array_out[] = $array_in; 
    }
}

$arr1 = array('1', '2', array(array(array('3'), '4', '5')), array(array('6')));

arrayFlatten($arr1, $arr2);

echo "<pre>";
print_r($arr2);
echo "</pre>";

您可以使用标准PHP库(SPL)来“隐藏”递归。

$a = array(1,2,array(3,4, array(5,6,7), 8), 9);
$it = new RecursiveIteratorIterator(new RecursiveArrayIterator($a));
foreach($it as $v) {
  echo $v, " ";
}

打印

1 2 3 4 5 6 7 8 9 

诀窍是通过引用传递源数组和目标数组。

function flatten_array(&$arr, &$dst) {
    if(!isset($dst) || !is_array($dst)) {
        $dst = array();
    }
    if(!is_array($arr)) {
        $dst[] = $arr;
    } else {
        foreach($arr as &$subject) {
            flatten_array($subject, $dst);
        }
    }
}

$recursive = array('1', array('2','3',array('4',array('5','6')),'7',array(array(array('8'),'9'),'10')));
echo "Recursive: \r\n";
print_r($recursive);
$flat = null;
flatten_array($recursive, $flat);

echo "Flat: \r\n";
print_r($flat);

// If you change line 3 to $dst[] = &$arr; , you won't waste memory,
// since all you're doing is copying references, and imploding the array 
// into a string will be both memory efficient and fast:)

echo "String:\r\n";
echo implode(',',$flat);

我需要用HTML输入格式表示PHP多维数组。

$test = [
    'a' => [
        'b' => [
            'c' => ['a', 'b']
        ]
    ],
    'b' => 'c',
    'c' => [
        'd' => 'e'
    ]
];

$flatten = function ($input, $parent = []) use (&$flatten) {
    $return = [];

    foreach ($input as $k => $v) {
        if (is_array($v)) {
            $return = array_merge($return, $flatten($v, array_merge($parent, [$k])));
        } else {
            if ($parent) {
                $key = implode('][', $parent) . '][' . $k . ']';

                if (substr_count($key, ']') != substr_count($key, '[')) {
                    $key = preg_replace('/\]/', '', $key, 1);
                }
            } else {
                $key = $k;
            }           

            $return[$key] = $v;
        }
    }

    return $return;
};

die(var_dump( $flatten($test) ));

array(4) {
  ["a[b][c][0]"]=>
  string(1) "a"
  ["a[b][c][1]"]=>
  string(1) "b"
  ["b"]=>
  string(1) "c"
  ["c[d]"]=>
  string(1) "e"
}