array_unique后，数组本身的值并不会变

<?php
$arr = [
    '',    '',    '',    '',    '',    '',    '',    '',    ''
       ];
print_r($arr);
print_r(array_unique($arr));
print_r($arr);　　　　　　　　//array_unique后，数组本身的值并不会变

?>

Array
(
    [] =>
    [] =>
    [] =>
    [] =>
    [] =>
    [] =>
    [] =>
    [] =>
    [] =>
)
Array
(
    [] =>
)
Array
(
    [] =>
    [] =>
    [] =>
    [] =>
    [] =>
    [] =>
    [] =>
    [] =>
    [] =>
)