Array functions in PHP8: multiple uses of array_unique()

In the PHP programming language, arrays are a very common data type. The unique thing about arrays is that they allow us to store multiple related variables at once, and these variables can be manipulated and processed efficiently. In PHP8, there are many useful array functions that can help us optimize our code, one of which is array_unique().

The array_unique() function is to remove duplicate array elements and return a new array. This function can be used in many situations. Below we will introduce some of the various uses of the array_unique() function.

1. Remove duplicate elements

The most basic usage is to remove duplicate elements in a numeric array or associative array. For example, we have an array with some duplicate elements:

$fruits = array("banana", "apple", "orange", "banana", "apple");

We can use the array_unique() function to remove the duplicate elements:

$unique_fruits = array_unique($fruits);

Now, the $unique_fruits array only contains The three elements "banana", "apple" and "orange" are included. This is a very common usage, especially when working with data fetched from a database.

2. Get the key name of the unique value in the array

The array_unique() function can also return a new array containing each unique value in the original array key name. For example, suppose we have the following array:

$colors = array("red", "green", "blue", "red", "green");

If we only want to get the key names of unique values ​​in the array, that is, "red", "green" and "blue", we can use the following code:

$unique_colors = array_unique($colors, SORT_REGULAR);
$unique_keys = array_keys($unique_colors);

In this way, the elements in the $unique_keys array are the key names of different elements in the original array $colors.

3. Merge arrays and remove duplicate elements

Suppose we have two numerical arrays, $numbers1 and $numbers2, and we want to merge them into one array, and To remove duplicate elements, you can use the array_unique() function:

$numbers1 = array(1, 3, 5, 2, 4);
$numbers2 = array(2, 4, 6, 8, 10);
$unique_numbers = array_unique(array_merge($numbers1, $numbers2));

Now, the $unique_numbers array contains all the elements in the two arrays, and the duplicate elements are removed.

4. Remove undefined elements in the array

When processing form submissions, sometimes we only want to retain some specific data submitted by the user. For example, we may want to keep only the name, email, and phone number from a form submission and delete other unnecessary data. At this time, you can define an array containing the elements that need to be retained, and then use the array_filter() and array_intersect_key() functions to remove undefined elements.

// 只保留姓名、邮箱和电话号码
$allowed_keys = array('name', 'email', 'phone');
$user_data = $_POST;
$filtered_data = array_filter(array_intersect_key($user_data, array_flip($allowed_keys)));

// 去除数组中的重复元素
$unique_data = array_unique($filtered_data);

In this way, the $unique_data array only contains the name, email and phone number submitted by the user, and duplicate elements are removed.

Summary

The above are the various uses of the array_unique() function. Whether it is to remove duplicate elements in an array, get unique key names in an array, merge arrays and remove duplicate elements, or keep only the elements we need in the array, the array_unique() function can come in handy.

It should be noted that when using the array_unique() function, if we do not specify the sorting method, it will automatically select the sorting method based on the type of the value. By default, it uses the SORT_STRING method to sort strings and the SORT_NUMERIC method to sort numbers. Therefore, special attention is required when using it.

In short, in PHP programming, the array_unique() function is a very practical array function. Proficient in its various uses can help us be more efficient and accurate when processing arrays.

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