，这种多维数组怎么输出呢

Array
(
    [0] => Array
        (
            [url] => http://127.0.0.1/show.php?id=6638
        )

    [1] => Array
        (
            [url] => http://127.0.0.1/show.php?id=6637
        )

    [2] => Array
        (
            [url] => http://127.0.0.1/show.php?id=6636
        )

    [3] => Array
        (
            [url] => http://127.0.0.1/show.php?id=6635
        )

    [4] => Array
        (
            [url] => http://127.0.0.1/show.php?id=6634
        )

    [5] => Array
        (
            [url] => http://127.0.0.1/show.php?id=6633
        )

    [6] => Array
        (
            [url] => http://127.0.0.1/show.php?id=6632
        )

    [7] => Array
        (
            [url] => http://127.0.0.1/show.php?id=6631
        )

    [8] => Array
        (
            [url] => http://127.0.0.1/show.php?id=6630
        )

    [9] => Array
        (
            [url] => http://127.0.0.1/show.php?id=6629
        )

    [10] => Array
        (
            [url] => http://127.0.0.1/show.php?id=6628
        )

    [11] => Array
        (
            [url] => http://127.0.0.1/show.php?id=6627
        )

    [12] => Array
        (
            [url] => http://127.0.0.1/show.php?id=6626
        )

    [13] => Array
        (
            [url] => http://127.0.0.1/show.php?id=6625
        )

    [14] => Array
        (
            [url] => http://127.0.0.1/show.php?id=6624
        )

    [15] => Array
        (
            [url] => http://127.0.0.1/show.php?id=6623
        )

    [16] => Array
        (
            [url] => http://127.0.0.1/show.php?id=6622
        )

    [17] => Array
        (
            [url] => http://127.0.0.1/show.php?id=6621
        )

    [18] => Array
        (
            [url] => http://127.0.0.1/show.php?id=6620
        )

)

http://127.0.0.1/show.php?id=6638
http://127.0.0.1/show.php?id=6637
http://127.0.0.1/show.php?id=6636
http://127.0.0.1/show.php?id=6635
http://127.0.0.1/show.php?id=6634
http://127.0.0.1/show.php?id=6633
http://127.0.0.1/show.php?id=6632
http://127.0.0.1/show.php?id=6631
http://127.0.0.1/show.php?id=6630
http://127.0.0.1/show.php?id=6629
http://127.0.0.1/show.php?id=6628
http://127.0.0.1/show.php?id=6627
http://127.0.0.1/show.php?id=6626
http://127.0.0.1/show.php?id=6625
http://127.0.0.1/show.php?id=6624
http://127.0.0.1/show.php?id=6623
http://127.0.0.1/show.php?id=6622
http://127.0.0.1/show.php?id=6621
http://127.0.0.1/show.php?id=6620

var_dump(array_column($data,'url'));

if(! function_exists('array_column')) :
  function array_column($input, $column_key, $index_key=null) {
    $res = array_map(function($tmp) use ($column_key) { return $tmp[$column_key]; }, $input);
    if(! empty($index_key)) $res =  array_combine(array_column($input, $index_key), $res);
    return $res;
  } 
endif;

$records = array(
    array(
        'id' => 2135,
        'first_name' => 'John',
        'last_name' => 'Doe',
    ),
    array(
        'id' => 3245,
        'first_name' => 'Sally',
        'last_name' => 'Smith',
    ),
    array(
        'id' => 5342,
        'first_name' => 'Jane',
        'last_name' => 'Jones',
    ),
    array(
        'id' => 5623,
        'first_name' => 'Peter',
        'last_name' => 'Doe',
    )
);
 
$first_names = array_column($records, 'id');//'first_name');
print_r($first_names);
$last_names = array_column($records, 'last_name', 'id');
print_r($last_names);

Array
(
    [0] => 2135
    [1] => 3245
    [2] => 5342
    [3] => 5623
)
Array
(
    [2135] => Doe
    [3245] => Smith
    [5342] => Jones
    [5623] => Doe
)