Tips for handling empty values ​​and null values ​​when deduplicating PHP arrays

Tips for handling empty and null values ​​when deduplicating PHP arrays: Use array_unique with array_filter to filter out empty and null values. Use array_unique and define a custom comparison function that treats null and null values ​​as equal. Use array_reduce to iterate over an array and add items if they do not contain empty or null values.

Tips for handling empty values ​​and null values ​​when deduplicating PHP arrays

Question

When clearing duplicates in an array, you need to consider how to handle empty and null values. By default, empty strings and null values ​​are treated as different values, which can lead to unexpected duplicates.

Tips

Three common techniques for handling empty and null values:

1. Use array_uniqueFunction collocationarray_filterFunction:

$arr = ['red', 'blue', 'green', null, '', 'red'];

$filtered_arr = array_filter($arr);
$result = array_unique($filtered_arr);

2. Use the array_unique function and define a custom comparison function:

$arr = ['red', 'blue', 'green', null, '', 'red'];

function cmp($a, $b) {
    return $a === $b;
}

$result = array_unique($arr, SORT_REGULAR, 'cmp');

3. Use array_reduce function:

$arr = ['red', 'blue', 'green', null, '', 'red'];

$result = array_reduce($arr, function($carry, $item) {
    if (!in_array($item, $carry) || $item !== '') {
        $carry[] = $item;
    }
    return $carry;
}, []);

Actual case

The following example demonstrates using the first technique to filter and deduplicate an array containing empty and null values:

$users = [
    ['name' => 'John Doe', 'age' => 30],
    ['name' => 'Jane Doe', 'age' => 25],
    ['name' => 'John Doe', 'age' => 30], // 重复项
    ['name' => null, 'age' => null], // 空值
];

$unique_users = array_filter($users);
$unique_users = array_unique($unique_users);

print_r($unique_users);

Output:

Array
(
    [0] => Array
        (
            [name] => John Doe
            [age] => 30
        )
    [1] => Array
        (
            [name] => Jane Doe
            [age] => 25
        )
)

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