How to remove duplicate elements from an array in php

In PHP development, deduplication is a basic operation, especially when dealing with arrays. Duplicate elements in the array will affect the performance of the program and the accuracy of the results, so the array needs to be deduplicated. This article will introduce how to use PHP to remove duplicate elements from an array.

The first method: use the array_unique() function

The array_unique() function is the most commonly used function for deduplication operations in PHP. It can delete duplicate elements in an array and return a new array. The following is an example code for using the array_unique() function to remove duplicates:

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

The output result is:

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

It can be seen that after using the array_unique() function to remove duplicates, the duplicate elements in the array are deleted.

Second method: Use loop traversal to remove duplicates

Another common deduplication method is to use a loop to traverse the array, and use the in_array() function to determine whether there are duplicate elements. In the case of duplicate elements, use the unset() function to delete the duplicate elements. The following is a sample code that uses loop traversal to remove duplicates:

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

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

print_r($new_array);

The output result is the same as the result after using the array_unique() function to remove duplicates.

The third method: use the array_flip() and array_keys() functions to remove duplicates

The last method to remove duplicates is to use the array_flip() function to use the values ​​in the array as keys and the keys As a value, duplicate values ​​can be deduplicated. Then use the array_keys() function to obtain the deduplicated key names, and the final result is the deduplicated array. The following is a sample code that uses the array_flip() and array_keys() functions to remove duplicates:

$array = array(1, 2, 2, 3, 4, 4, 5);

$array_flip = array_flip($array);
$array_keys = array_keys($array_flip);

print_r($array_keys);

The output result is also the same as the result after using the array_unique() function to remove duplicates.

The above three methods can remove duplicate elements in the array. The array_unique() function is the most commonly used method because it is simple and easy to use and has good efficiency. For scenarios where large arrays need to be deduplicated, memory can be saved by using a loop to deduplicate. The performance loss caused by using the in_array() function can be avoided by using the array_flip() and array_keys() functions to remove duplicates.

In actual development, it is very important to choose different deduplication methods according to different scene requirements.

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