PHP removes the same array

When developing in PHP, we usually need to operate on arrays. One of the common problems is how to remove the same elements in the array. The same elements will affect our data statistics and processing, so duplication needs to be removed before normal data analysis can be performed. But how to remove identical elements from an array? This article will introduce some different ways to solve this problem.

Method 1: Use PHP’s array_unique() function

The array_unique() function is a built-in function in PHP, used to remove duplicate elements from an array. This function returns a new array containing all the distinct values ​​in the original array. The following is an example:

// 定义一个有重复元素的数组
$array = array(1, 2, 2, 3, 4, 4, 5);

// 使用array_unique()函数去重
$new_array = array_unique($array);

// 输出结果
print_r($new_array);

Running the above code will output the following results:

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

As you can see, the array_unique() function removes all duplicate elements and returns a new array .

Method 2: Use PHP’s array_flip() and array_keys() functions

Another way to remove duplicates is to use the array_flip() and array_keys() functions. The array_flip() function can exchange the keys and values ​​in the array, while the array_keys() function can return the values ​​of all keys in the array. Therefore, we can use these two functions to remove duplicate elements from the array. Here is an example:

// 定义一个有重复元素的数组
$array = array(1, 2, 2, 3, 4, 4, 5);

// 使用array_flip()和array_keys()函数去重
$new_array = array_keys(array_flip($array));

// 输出结果
print_r($new_array);

Running the above code will get the same results as the previous example.

Method 3: Use loop comparison

In addition to using built-in functions, we can also use loop comparison to remove duplicates. The principle of this method is to traverse each element in the array, compare it with all previous elements in the array, if it is the same as the previous element, skip it, otherwise add it to the new array. Here is an example:

// 定义一个有重复元素的数组
$array = array(1, 2, 2, 3, 4, 4, 5);

// 使用循环对比的方法去重
$new_array = array();
foreach($array as $item) {
    if(!in_array($item, $new_array)) {
        $new_array[] = $item;
    }
}

// 输出结果
print_r($new_array);

Running the above code will yield the same results as the first two examples.

Summary

The above are three commonly used deduplication methods. When choosing a method, consider data size as well as code efficiency. If the data size is relatively small, we can use any method; but if the data size is very large, efficiency becomes an important issue. At this time, the most efficient method should be used to remove duplicates to avoid the program running too slowly. No matter which method is used, deduplication is a common operation in program development and requires us to master it skillfully.

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