PHP array value and key interchange: implementation and performance comparison

In PHP, array keys and values ​​can be exchanged through the following methods: array_flip() function: simple syntax, direct key-value exchange, time complexity O(n). Custom function: flexible and can be customized according to needs, but the time complexity is also O(n). Shift operators: Requires PHP knowledge, more efficient in some cases, still O(n) time complexity.

PHP array value and key exchange: implementation and performance comparison

In PHP, it is often necessary to exchange the array key and value so that for further processing. There are multiple ways to do this, each with its pros and cons.

Method 1: array\_flip() function

array_flip() The function is a built-in function provided by PHP that is directly used to exchange array values ​​and keys. Using it is very simple, just pass the original array as a parameter:

$originalArray = [
    'name' => 'John Doe',
    'age' => 30,
];

$flippedArray = array_flip($originalArray);

print_r($flippedArray);

Output:

Array
(
    [John Doe] => name
    [30] => age
)

Method 2: Custom function

You can also define a custom one function to interchange array values ​​and keys:

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

This custom function works similarly to the array_flip() function, but it provides greater flexibility. For example, you can add additional logic to handle special cases or modify the output format as needed.

Method 3: Displacement operator

The displacement operator (=>) can also be used to interchange array keys and values. This approach requires a certain level of PHP knowledge, but it may be more efficient than others in some cases:

$originalArray = [
    'name' => 'John Doe',
    'age' => 30,
];

$flippedArray = [];
foreach ($originalArray as $key => $value) {
    $flippedArray[$value] = $key;
}

Practical Case

Suppose there is a An array of product information, whose price needs to be obtained based on the product name. Arrays can be quickly transformed using value and key swapping to easily find the price data you need:

$products = [
    'Apple' => 10,
    'Orange' => 5,
];

// 使用 array_flip() 互换键和值
$flippedProducts = array_flip($products);

// 根据产品名称获取价格
$price = $flippedProducts['Orange'];

In the above example, $price will now contain the product Orange price without traversing the entire original array to find it.

Performance comparison

Here is a quick comparison of performance when using different methods to swap arrays:

O(n)Custom functionO(n)Shift operatorO(n)

Method	Time complexity
##array_flip()

It should be noted that the performance complexity is the same for all methods because they all need to traverse the entire array. Therefore, which method to choose depends on the specific use case and the developer's personal preference.

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