How to remove duplicate elements from PHP array

In PHP, an array is a commonly used data structure that can hold multiple values. Sometimes, we need to filter out some elements from the array. At this time, we can use some functions in PHP to achieve this. Here's how to remove duplicate elements from a PHP array.

1. Use the array_unique function

The array_unique function can remove duplicate elements in the array, retaining only the first appearing element, and all other duplicate elements are deleted. The usage is as follows:

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

The output result is:

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

It can be seen that the function array_unique successfully removes duplicate elements in the array.

2. Use the array_flip and array_keys functions

If you want to remove duplicate elements in an array and retain the key names of all elements, you can use the array_flip and array_keys functions. The specific method is as follows:

$array = array(1, 2, 3, 2, 1);
$array = array_flip($array);
$array = array_keys($array);
print_r($array);

The output result is:

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

It can be seen that after processing by these two functions, the duplicate elements in the array are removed and all elements are retained. key name.

3. Using a loop to traverse the array

In addition to the above two methods, you can also use a loop to traverse the array to achieve the function of removing duplicate elements. The specific method is as follows:

$array = array(1, 2, 3, 2, 1);
$new_array = array();
foreach ($array as $value) {
    if (!in_array($value, $new_array)) {
        $new_array[] = $value;
    }
}
print_r($new_array);

The output result is:

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

By looping through the array and using the in_array function to determine whether it already exists, you can effectively remove duplicate elements in the array.

To sum up, there are many methods in PHP to remove duplicate elements from an array. Choosing the appropriate method according to actual needs can make code development more convenient and efficient.

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