How to change key value in array using PHP

PHP, as a widely used programming language, has a very wide range of application scenarios in application development. In PHP, developers often need to save data of different data types into arrays. When processing these array data, changing the key values ​​in the array is a common requirement. In this article, we will explain how to change the key value in an array using PHP.

What is an array?

In PHP, an array is a data structure used to save and manage multiple data. Common array types include indexed arrays, associative arrays, and multidimensional arrays. Among them, an indexed array is an array that stores values ​​in numerical index order. Associative arrays are arrays that use string keys to store values, while multidimensional arrays are particularly structured array types.

How to create an array?

In PHP, there are many ways to create arrays. Here are some examples of creating arrays:

//创建一个空数组
$arr1 = array();

//创建一个索引数组
$arr2 = array(1, 2, 3, 4, 5);

//创建一个关联数组
$arr3 = array('name'=>'Jack','age'=>20,'gender'=>'man');

//创建一个多维数组
$arr4 = array(
    array('name'=>'Jack','age'=>20,'gender'=>'man'),
    array('name'=>'Rose','age'=>18,'gender'=>'woman')
);

How to change the key values ​​in an array?

Modifying key values ​​in an array is a common requirement in PHP. We can change the key value in the array through the following two methods:

Method 1: Use the language structure unset() and the array addition operator =

Use the language structure unset() and the array Adding operator = can change any key name (key value) in the array. Among them, unset is used to delete the old key name, and then add the operator = to the array to add the new key name. The following is a sample code:

//使用unset()和+=更改关联数组arr3中标记为'name'的键
unset($arr3['name']);  
$arr3 += array('new_name'=>'Tom');

//使用unset()和+=更改索引数组arr2中第2个位置的键
unset($arr2[1]);  
$arr2 += array(1=>'new_value');

The condition for using the above method is that the name of the key to be changed must be known in advance, which does not apply when the number of keys in the array is large.

Method 2: Use array_map() and anonymous functions

Using array_map() and anonymous functions can more easily modify certain key names in the array. First, define an anonymous function that converts the input key name into a new key name and returns a new array as the result. Then, use the array_map() function on each key name in the array to make changes to all keys in the array. The following is sample code:

//使用array_map()和匿名函数更改关联数组中的键名
$function = function($key){ 
    switch($key){
        case 'name': 
            return 'new_name';
        case 'age': 
            return 'new_age'; 
        default: 
            return $key;
    } 
}; 

$arr_new = array_map($function,$arr3);

When using the above method, you need to note that the value returned in the anonymous function is the new key name. In this way, all key names in the array can be changed without knowing the key names.

Summary

In PHP data processing, changing the key name in an array is probably one of the most common needs. In this article, we teach two methods to implement this function. In specific actual situations, developers can choose a suitable method to implement based on actual needs. Proficiency in modifying key names in arrays is a very important skill for PHP developers.

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