How to achieve deduplication of data in PHP arrays?

Three methods to deduplicate PHP arrays: use the array_unique() function to remove duplicate values ​​based on element values ​​and retain the key value order. Use the array_filter() function to remove duplicate elements based on conditions in a callback function. Use the SplObjectStorage class to take advantage of the uniqueness of objects to achieve array deduplication and retain key-value associations.

How to achieve deduplication of data in PHP arrays

Array deduplication refers to removing duplicate values ​​in the array and obtaining a new one containing only unique values. array. PHP provides several methods to achieve array deduplication:

Use array_unique() Function

array_unique() is a built-in function, specifically Used to remove duplicate values ​​from an array. It compares based on the value of each element and returns a new array containing only unique elements. The syntax is as follows:

array_unique(array $array);

Example:

$numbers = [1, 2, 3, 4, 5, 1, 2, 3];
$unique_numbers = array_unique($numbers);
print_r($unique_numbers);

Output:

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

Note: array_unique() The key value order will be preserved, but if necessary, you can use the array_values() function to change the preserved key values ​​into consecutive numbers.

Use array_filter() Function

array_filter() The function can remove certain elements from the array based on the conditions of the callback function. It will keep the elements that satisfy the callback function's return true in the array, and filter out other elements.

Example:

$numbers = [1, 2, 3, 4, 5, 1, 2, 3];
$unique_numbers = array_filter($numbers, function($value, $index) {
    return array_search($value, $numbers) === $index;
});
print_r($unique_numbers);

Output:

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

Note: This callback function checks the occurrence of each element in the array Whether the first index is the same as the current index to determine if it is a unique value.

Using SplObjectStorage Class

SplObjectStorage class is a more advanced container for storing a collection of objects. You can use it as a hash table, where the objects are the keys and the associated values ​​are the retained values. Since hash tables do not allow duplicate keys, SplObjectStorage can be used to achieve array deduplication.

Example:

$numbers = [1, 2, 3, 4, 5, 1, 2, 3];
$unique_numbers = new SplObjectStorage();

foreach ($numbers as $number) {
    $unique_numbers->attach($number);
}

foreach ($unique_numbers as $number) {
    echo $number . "\n";
}

Output:

1
2
3
4
5

Note: This method takes advantage of the fact that objects cannot be repeated. The keys in SplObjectStorage are not unique because each object has a different identity. Therefore, it can effectively remove duplicate values ​​from the array.

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