PHP array key-value exchange: Strategies and performance comparison of multi-dimensional array key-value exchange

In PHP, you can use the array_flip() function to exchange one-dimensional array key values, and for multi-dimensional arrays, there are multiple strategies to choose from. Recursive strategies are suitable for processing nested multidimensional arrays, but recursion may cause function stack overflow. The iterative strategy avoids this problem, but is less efficient for more nested arrays. Depending on the array size and structure, choose a recursive or iterative strategy for best performance.

PHP array key-value exchange: strategy and performance comparison of multi-dimensional array key-value exchange

In PHP, sometimes The keys and values ​​of the array need to be interchanged. For one-dimensional arrays, this is as simple as using the array_flip() function. However, for multidimensional arrays, the situation becomes complicated.

Strategy and Performance Comparison

There are various strategies that can be used to exchange the key values ​​of multi-dimensional arrays, and each strategy has its advantages and disadvantages. Here are the two most commonly used strategies:

1. Use recursion

function flipArrayRecursive(array $array) {
    if (!is_array($array)) {
        return $array;
    }

    $flippedArray = [];
    foreach ($array as $key => $value) {
        $flippedArray[$value] = flipArrayRecursive($key);
    }
    return $flippedArray;
}

Advantages:When dealing with nested multi-dimensional arrays, recursion The strategy is very effective.

Disadvantages: Recursion may cause function stack overflow, especially when dealing with very large arrays.

2. Use iteration

function flipArrayIterative(array $array) {
    $flippedArray = [];

    $queue = new SplQueue();
    $queue->enqueue([$array, null]);

    while (!$queue->isEmpty()) {
        list($currentArray, $parentKey) = $queue->dequeue();

        foreach ($currentArray as $key => $value) {
            if (is_array($value)) {
                $queue->enqueue([$value, $key]);
            } else {
                $flippedArray[$value] = $parentKey === null ? $key : "$parentKey.$key";
            }
        }
    }

    return $flippedArray;
}

Advantages:The iteration strategy avoids the function stack overflow problem and works well even for larger arrays work.

Disadvantages: When dealing with nested multidimensional arrays, the iteration strategy may become slower as the depth of the array increases.

Practical Case

Consider a scenario: you need to convert a two-dimensional array containing key-value pairs into a two-dimensional array containing value key pairs.

Original array:

$array = [
    'key1' => 'value1',
    'key2' => 'value2',
    'key3' => ['key3-1' => 'value3-1', 'key3-2' => 'value3-2']
];

Use recursive strategy to get the swapped array:

$flippedArray = flipArrayRecursive($array);

Output:

Array
(
    [value1] => key1
    [value2] => key2
    [value3-1] => key3.key3-1
    [value3-2] => key3.key3-2
)

Use iteration strategy to obtain the swapped array:

$flippedArray = flipArrayIterative($array);

Output:

Array
(
    [value1] => key1
    [value2] => key2
    [value3-1] => key3.key3-1
    [value3-2] => key3.key3-2
)

Which strategy to choose?

The choice of the best strategy depends on the size and structure of the array. For smaller arrays or less nested arrays, a recursive strategy may be more efficient. For larger arrays or more nested arrays, an iterative strategy is more appropriate.

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