Remove Duplicates While Preserving Original Keys (First Occurrence)

function remove_duplicates_preserve_keys(array $array): array {
    return array_reverse(array_flip(array_reverse($array)));
}

$data = [
    'a' => 'apple',
    'b' => 'banana',
    'c' => 'apple',
    'd' => 'orange',
    'e' => 'banana',
    'f' => 'grape'
];

$uniqueData = remove_duplicates_preserve_keys($data);
print_r($uniqueData);
/* Output:
Array
(
    [a] => apple
    [b] => banana
    [d] => orange
    [f] => grape
)*/

How it works: This clever snippet removes duplicate values from an array while preserving the original keys associated with the *first* occurrence of each unique value. It achieves this using a combination of `array_reverse` and `array_flip`. The first `array_reverse` places the last occurrences of values at the beginning. `array_flip` then uses these values as keys; since keys must be unique, duplicate values overwrite previous entries. Finally, `array_reverse` is called again to restore the original order, effectively keeping only the first occurrence of each value along with its original key.