如何复制php数组中的每个键

<?php
$array = array('key1' => 'value1', 'key2' => 'value2', 'key3' => 'value3');

$keys = array_keys($array);
$values = array_values($array);

$copyArray = array_combine($keys, $values);

print_r($copyArray);
?>

Array
(
    [key1] => value1
    [key2] => value2
    [key3] => value3
)