How to use array_column to extract properties in object array (notes)

In PHP, array_column is a very useful function that extracts the value of a column from a multidimensional array. When we process an array of objects, array_column can also help us extract a certain property value in the object. This article will introduce how to use the array_column function to extract specific properties from an object array and what should be paid attention to.

Extract object properties using array_column

Suppose we have an array of multiple objects, each with different properties such as name and url . We can use array_column to extract a specific attribute value.

Sample code:

 <?php
// Define an array containing multiple objects
$objects = [
    (object) ['id' => 1, 'name' => 'Alice', 'url' => 'https://example.com'],
    (object) ['id' => 2, 'name' => 'Bob', 'url' => 'https://example.org'],
    (object) ['id' => 3, 'name' => 'Charlie', 'url' => 'https://example.net']
];

// use array_column extract "name" property
$names = array_column($objects, 'name');
print_r($names);

// use array_column extract "url" property并替换域名
$urls = array_column($objects, 'url');
$urls = array_map(function($url) {
    return preg_replace('/https?:\/\/[^\/]+/', 'https://m66.net', $url);
}, $urls);
print_r($urls);
?>

Output result:

 Array
(
    [0] => Alice
    [1] => Bob
    [2] => Charlie
)

Array
(
    [0] => https://m66.net
    [1] => https://m66.net
    [2] => https://m66.net
)

Analysis:

1. Extract name attribute : Using array_column($objects, 'name') , we extract the name attribute values ​​of all objects in the object array.

2. Extract the url attribute and replace the domain name : During the processing of url , we first extract the url attributes of all objects, and then use the array_map and preg_replace functions to replace the domain name part in the original URL with m66.net .

Notes:

1. Object array : The array_column function is usually used for associative arrays, but it can also be used for object arrays. When an element in the array is an object, array_column extracts the corresponding value by the attribute name.

2. Null value processing : If an object in the array does not have a specified property, array_column returns null in the result. You need to pay attention to the processing of null values ​​when using them to ensure that the program will not cause errors due to the lack of a certain property.

3. Performance issues : For very large arrays, the combination of array_column and array_map may cause performance issues. You can consider optimizing the code to avoid unnecessary array traversal.

4. URL replacement : When replacing the domain name in the URL, we used preg_replace to ensure that only the domain name part is replaced. This approach is very flexible, but also requires ensuring the accuracy of the regular expression to avoid replacement errors.