How to remove identical elements from an array in php

PHP is a widely used scripting language commonly used to build dynamic websites and web applications. In the PHP development process, it is very important to process and operate arrays, because arrays in PHP are a flexible and easy-to-use data structure that can store multiple types of data, such as numbers, strings, objects, etc. However, when the same elements exist in the array, we need to remove these duplicate data in order to better process and analyze the data. This article will introduce several methods to remove duplicate elements from PHP arrays.

Method 1: array_unique() function

The array_unique() function is a function provided by PHP for removing duplicate elements from an array. It takes an array as argument and returns a new array containing only the unique elements from the original array.

The following is a sample code:

$arr = array(1, 2, 3, 3, 4, 4, 5);
$new_arr = array_unique($arr);
print_r($new_arr);

Run the above code, the output result is as follows:

Array
(
    [0] => 1
    [1] => 2
    [2] => 3
    [4] => 4
    [6] => 5
)

As you can see, the repeated elements 3 and 4 in the original array $arr are Removed successfully. This method is very simple and easy to use and suitable for general deduplication operations.

Method 2: Use PHP built-in functions array_flip() and array_keys()

array_flip() function can exchange the keys and values ​​​​in the array and return a new array so that the old keys becomes the value, and the old value becomes the key. The array_keys() function can return all the key names in the array.

We can first use the array_flip() function to exchange the keys and values ​​of the array and get a new array. Then use the array_keys() function to get all the key names in this new array, and finally return an array of key names after removing duplicate elements.

The sample code is as follows:

$arr = array(1, 2, 3, 3, 4, 4, 5);
$new_arr = array_flip($arr);

//获取新数组中的所有键名
$new_arr = array_keys($new_arr);

print_r($new_arr);

Run the above code, the output result is as follows:

Array
(
    [0] => 1
    [1] => 2
    [2] => 3
    [3] => 4
    [4] => 5
)

This method is slightly more troublesome than the array_unique() function, but the speed will be Faster and suitable for processing large arrays.

Method 3: Use a loop to traverse and compare

In addition to the above two methods, we can also use a loop to traverse the array and compare the values ​​of the elements one by one to remove duplicate elements. The implementation process of this method is relatively complex, but it is also very flexible.

The sample code is as follows:

$arr = array(1, 2, 3, 3, 4, 4, 5);
$new_arr = array();

foreach ($arr as $value) {
    if (!in_array($value, $new_arr)) {
        $new_arr[] = $value;
    }
}

print_r($new_arr);

In the above code, we first create a new empty array $new_arr. Then use a foreach loop to traverse each element in the original array $arr, and use the in_array() function to determine whether the element appears in the new array. If it does not appear before, the element is added to the new array. If it has already appeared, skip the element directly.

Run the above code, the output result is as follows:

Array
(
    [0] => 1
    [1] => 2
    [2] => 3
    [3] => 4
    [4] => 5
)

This method is more flexible and can be modified according to actual needs. Also, it may be slower when working with large arrays due to the need to loop through the entire array.

To sum up, there are many methods to choose from in PHP to remove duplicate elements from an array. We can choose different methods according to actual needs to achieve the best results. In actual development, you can choose the most suitable method for deduplication based on the amount of data and requirements.

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