PHP array key-value exchange: a comprehensive analysis from principle to practice

PHP array key-value exchange principle: exchange keys and values ​​to generate a new array. The implementation method is: use the array_flip() function: swap the key values ​​and return a new array. Use the array_combine() function: Create a new array with arrays as keys and values.

PHP Array Key Value Interchange: Comprehensive Analysis from Principle to Practice

In PHP, array is a basic A data structure that can be used to store data and access elements by key. Sometimes, we need to interchange the keys and values ​​of the array to meet different needs.

Principle

The principle of array key-value exchange is very simple: store the value of each key as a new value, and store each value as a new key. For example, for the array ['foo' => 'bar', 'baz' => 'qux'], the array after swapping the keys will be ['bar' =&gt ; 'foo', 'qux' => 'baz'].

Syntax

PHP provides a variety of methods to interchange the keys and values ​​of an array. The two most common methods are:

• array_flip() function: Exchange the keys and values ​​of the array and return a new array. Syntax: array_flip($array)
• array_combine() Function: Create a new array using one array as the key and another array as the value. Syntax: array_combine($keys, $values)

Practical case

Case 1: Using array_flip() function

Suppose we have an array with user ID as key and username as value:

$users = [
    1 => 'John Doe',
    2 => 'Jane Smith',
    3 => 'Bob Jones',
];

Use the array_flip() function to swap key values, With username as key and user ID as value:

$flippedUsers = array_flip($users);

Now, $flippedUsers will contain the following key-value pairs:

[
    'John Doe' => 1,
    'Jane Smith' => 2,
    'Bob Jones' => 3,
]

Case 2: Using array_combine () Function

Suppose we have two arrays, one containing fruit names and the other containing fruit prices:

$fruits = ['Apple', 'Banana', 'Orange'];
$prices = [10, 15, 20];

Use the array_combine() function to combine the fruits Pair the name with the price, creating a new associative array:

$fruitPrices = array_combine($fruits, $prices);

Now, $fruitPrices will contain the following key-value pairs:

[
    'Apple' => 10,
    'Banana' => 15,
    'Orange' => 20,
]

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