PHP：在多维数组中使用变量作为多个键

Question

在普通数组中你可以这样选择

$key='example';
echo $array[$key];

多维情况如何？

$keys='example[secondDimension][thirdDimension]';
echo $array[$keys];

解决这个问题的正确方法是什么？

Answer 1

我认为这个解决方案很好。

注意你必须用“[”和“]”包裹所有的键。

$array = array(
    'example' => array(
        'secondDimension' => array(
            'thirdDimension' => 'Hello from 3rd dimension',
        )
    ),
);

function array_get_value_from_plain_keys($array, $keys)
{
    $result;

    $keys = str_replace(array('[', ']'), array("['", "']"), $keys); // wrapping with "'" (single qoutes)

    eval('$result = $array' . $keys . ';');

    return $result;
}

$keys = '[example][secondDimension][thirdDimension]'; // wrap 1st key with "[" and "]"
echo array_get_value_from_plain_keys($array, $keys);

了解有关 eval() 函数的更多信息

如果您还想检查该值是否已定义，则可以使用此功能

function array_check_is_value_set_from_plain_keys($array, $keys)
{
    $result;

    $keys = str_replace(array('[', ']'), array("['", "']"), $keys); // wrapping with "'" (single qoutes)

    eval('$result = isset($array' . $keys . ');');

    return $result;
}

给那个函数一个更好的名字将不胜感激^^

Answer 2

这里有一个不使用 eval 的解决方案：

$array = [
    'example' => [
        'secondDimension' => [
            'thirdDimension' => 'Hello from 3rd dimension',
        ],
    ],
];

$keys = '[example][secondDimension][thirdDimension]';

function get_array_value( $array, $keys ) {
    $keys = explode( '][', trim( $keys, '[]' ) );

    return get_recursive_array_value( $array, $keys );
}

function get_recursive_array_value( $array, $keys ) {
    if ( ! isset( $array[ $keys[0] ] ) ) {
        return null;
    };
    $res = $array[ $keys[0] ];
    if ( count( $keys ) > 1 ) {
        array_shift( $keys );

        return get_recursive_array_value( $res, $keys );
    } else {
        return $res;
    }
}

echo get_array_value( $array, $keys );

Answer 3

希望你使用$b数组跟随$a数组的嵌套键并获取$c中的值？

<?php
$a = [ 'key_1' => [ 'key_2' => [ 'key_3' => 'value', ], ], ] ;
$b = ['key_1', 'key_2', 'key_3', ] ;
if ($b)
{
    $c = $a ; // $a is not copied (copy-on-write)
    foreach($b as $k)
        if (isset($c[$k]))
            $c = $c[$k] ;
        else
        {
            unset($c);
            break;
        }
    var_dump($c);
}
/*
output :
    string(5) "value"
*/

或者您想为任意形成的字符串生成 $b 数组并获取 $c 作为参考？

<?php
$a = [ 'key_1' => [ 'key_2' => [ 'key_3' => 'value', ], ], ] ;
$b = '[key_1][key_2][key_3]';
if ($b !== '')
{
    $b = explode('][', trim($b, '[]'));
    $c = &$a ;
    foreach($b as $k)
        if (isset($c[$k]))
            $c = &$c[$k] ;
        else
        {
            unset($c);
            break;
        }
}
var_dump($c);
$c = 'new val' ;
unset($c);
var_dump($a['key_1']['key_2']['key_3']);
/*
output :
    string(5) "value"
    string(7) "new val"
*/

Answer 4

我编写的使用 eval() 的简化示例，用于从 Shopify 客户数据数组中提取电话号码：

    // this is weird but whatever
    $arrayPaths = array(
        '[\'phone\']',
        '[\'addresses\'][0][\'phone\']',
        '[\'addresses\'][1][\'phone\']'
        );
    
    foreach ($arrayPaths as $path) {
        
        // hack to store/access multidimentional array keys as array, sets 
        // a variable named $phoneNumber
        $code = '$phoneNumber = $dataArray' . $path . ';';
        eval($code);
        var_dump($phoneNumber);
        
    }

Answer 5

你必须为数组的每个维度使用一个单独的变量。您在多维数组中看到的一个常见模式是，您需要对二维数组做一些事情是这样的：

$pets = [
    'dog' => ['Jack', 'Fido', 'Woofie'],
    'cat' => ['Muggles', 'Snowball', 'Kitty'],
];

// Loop through keys in first dimension
foreach ($pets as $type => $names) {

    foreach ($names as $index => $name) {

        // And do something with second dimension using the variable
        // you've gained access to in the foreach
        $pets[$type][$index] = strtoupper($name);

    }

}