解决 PHP 数组去重后元素顺序变化的问题

$array = ['a', 'b', 'c', 'a', 'd'];

$unique_array = array_intersect_key($array, array_unique($array));

$array = ['a', 'b', 'c', 'a', 'd'];

$unique_array = array();
$seen_keys = array_flip($array);

foreach ($seen_keys as $key => $val) {
    $unique_array[$key] = $array[$key];
}

$array = ['a', 'b', 'c', 'a', 'd'];

$unique_array = array_values(array_unique($array));

$array = ['red', 'green', 'blue', 'red', 'orange'];

$unique_array = array_unique($array); // ['green', 'blue', 'orange', 'red']

$unique_array_intersect = array_intersect_key($array, array_unique($array)); // ['red', 'green', 'blue', 'a']
$unique_array_flip = array();
$seen_keys = array_flip($array);
foreach ($seen_keys as $key => $val) {
    $unique_array_flip[$key] = $array[$key];
} // ['red', 'green', 'blue', 'a']
$unique_array_values = array_values(array_unique($array)); // ['red', 'green', 'blue', 'orange']