PHP array key value exchange: algorithm selection based on different data types

PHP The method of swapping array key values ​​varies depending on the data type: Associative arrays (string or integer keys): use the array_flip() function. Normal array (integer keys): Use asort() to sort the array, then use array_keys() to get the keys. Array of objects: Use array_map() and callback functions to map an object's properties into a new array.

PHP array key-value exchange: algorithm selection based on data type

In PHP, an array is an ordered And keyed data structure. Key-value exchange refers to exchanging the keys and values ​​of an array to form a new array. Depending on the data type of the elements in the array, there are different algorithms for key-value interchange.

Algorithm selection

Data type	Algorithm
Associative array (keys are strings or integers)	array_flip()
Ordinary array (keys are integers)	asort() array_keys()
Object array	array_map() Custom callback function

##Practical case

1. Associative array

$arr = ['name' => 'John', 'age' => 30];
$flippedArr = array_flip($arr);
print_r($flippedArr);
// 输出：
// Array
// (
//     [John] => name
//     [30] => age
// )

2. Ordinary array

$arr = [1, 2, 3, 4, 5];
asort($arr);
$flippedArr = array_keys($arr);
print_r($flippedArr);
// 输出：
// Array
// (
//     [0] => 1
//     [1] => 2
//     [2] => 3
//     [3] => 4
//     [4] => 5
// )

3. Object array

class Person {
    public $name;
    public $age;
}

$person1 = new Person();
$person1->name = 'John';
$person1->age = 30;

$person2 = new Person();
$person2->name = 'Mary';
$person2->age = 25;

$arr = [$person1, $person2];

$flippedArr = array_map(function ($obj) {
    return [$obj->name, $obj];
}, $arr);

print_r($flippedArr);
// 输出：
// Array
// (
//     ['John'] => Person Object
//         (
//             [name] => John
//             [age] => 30
//         )
//
//     ['Mary'] => Person Object
//         (
//             [name] => Mary
//             [age] => 25
//         )
// )

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