Combining array_diff_key() and array_map() to handle key name differences

M66 2025-06-06

How to use array_diff_key() and array_map() in combination to handle array key name differences and perform corresponding data processing?

In PHP, array_diff_key() and array_map() are two very commonly used array operation functions that can help developers process arrays more efficiently. array_diff_key() is used to compare the key names of an array, while array_map() is used to apply a callback function to each element of the array. When these two functions are used in combination, we can flexibly handle differences in array key names and perform corresponding data operations.

1. Introduction to array_diff_key() function

The array_diff_key() function is used to compare the key names of two (or more) arrays, returning elements corresponding to those key names in the first array but not in the other arrays. Its basic syntax is as follows:

 array_diff_key(array $array1, array $array2, array ...$arrays): array

$array1 : The first array.
$array2 : Other arrays used for comparison.

This function returns a new array containing the key names present in $array1 that do not exist in $array2 (or other array).

2. Introduction to array_map() function

The array_map() function is used to apply a callback function to each element in the array, returning a new array. Its basic syntax is as follows:

 array_map(callable $callback, array $array, array ...$arrays): array

$callback : The callback function applied to each element of the array.
$array : The array to operate.
The function will return a new array, each element in the array is the result of the callback function execution.

3. Use array_diff_key() and array_map() in combination

When we need to deal with the difference in key names in an array, array_diff_key() can help us find different key names between two arrays. Once we find the difference, we can use array_map() to process the values of these arrays accordingly.

Suppose we have two arrays: one is a complete array of user data, and the other is the data that needs to be filtered out. We hope that after deleting certain key names, we will further process the remaining data, such as formatting dates, converting values, etc.

4. Sample code

Here is a sample code that demonstrates how to use array_diff_key() and array_map() in combination to process key name differences in arrays and perform corresponding data processing.

 <?php

// Original user data array
$userData = [
    'id' => 1,
    'name' => 'John Doe',
    'email' => 'johndoe@example.com',
    'dob' => '1990-05-15',
    'address' => '123 Main St',
    'phone' => '555-1234'
];

// Array of key names to be removed
$removeKeys = [
    'phone' => true,
    'address' => true
];

// use array_diff_key() Delete the specified key name in the array
$filteredData = array_diff_key($userData, $removeKeys);

// use array_map() Process the remaining data，Format date
$processedData = array_map(function($value, $key) {
    // 假设我们只想Format date（dob）Value of
    if ($key == 'dob') {
        return date('Y-m-d', strtotime($value)); // Format date
    }
    return $value; // No processing for other fields
}, $filteredData, array_keys($filteredData));

// Print results
echo '<pre>';
print_r($processedData);

?>

5. Code parsing

First, we define an array $userData containing user information, and an array $removeKeys that specifies the key names to be removed.
Using the array_diff_key() function, we remove the key name from the $removeKeys array from $userData . This results in a $filteredData array containing the key names that need to be preserved and their corresponding values.
Then, use array_map() to process each element in the $filteredData array. In the callback function, we check each key name, and if it is 'dob' , it formats its value, converting the date to the specified format.
Finally, we use print_r() to output the processed array $processedData .

6. Handle URL domain name replacement

Assuming that a value in the array contains a URL, we can use array_map() to replace the URL's domain name during processing. For example, replace the domain names of all URLs with m66.net .

array_diff_key