将多维PHP数组转换为类似于表格的格式，并将键作为列

I have the following multidimensional array where the parent keys are long hashes, each of which contains a number of key=>value pairs which result in the following PHP data structure:

Array ( [riCQTaeQmczjR7ynRB30wzCghOhN3T82h9qXYl8M] => Array ( [Timestamp] => 2018-03-28 21:47:53 [What's your name?] => Alberto [When do you want to book] => tomorrow ) [wD5bb9lNTxmb3EftdenrO3UMJThMQ6mDhpKQFvjC] => Array ( [Timestamp] => 2018-03-28 21:48:10 [What's your name?] => AAA [When do you want to book] => next week ) [02tgD3iOH2pIyrku1m9uukwwFeISHis7C9TlMaPR] => Array ( [Timestamp] => 2018-03-28 23:30:16 [What's your name?] => Osvaldo [When do you want to book] => next week ) [aPjjcwhr2HeuFOaw3Jc0ijsf6C5VtAxOquSduIOP] => Array ( [Timestamp] => 2018-03-28 23:31:16 [What's your name?] => Jhonny [When do you want to book] => tomorrow ) )

The data structure above can be also visually represented as:

Notice that each one of the parent elements (i.e. long hashes) always contains the same keys as all the others (in this example each parent element contains 1 timestamp and 2 question-answer pairs).

My goal is to convert this multidimensional array into the following table-like format that can be easily exported in a csv file:

"Timestamp","What's your name?","When do you want to book?"
"2018-03-28 21:47:53","Lorna","tomorrow"
"2018-03-28 21:48:10","Jake","next week"
"2018-03-28 23:30:16","Sarah","next week"
"2018-03-28 23:31:16","Johnny","tomorrow"

The array keys become the "header", while each line represents one answer. I think one way to go would be using the PHP function array_map() but I wasn't able to achieve the desired result. Any idea / tip on how to do this?

<?php

$data = [
    [
        'Timestamp' => '2018-03-01',
        'What\'s your name?' => 'Johnny',
        'When do you want to book?' => 'tomorrow'
    ],
    [
        'Timestamp' => '2018-03-01',
        'What\'s your name?' => 'Johnny',
        'When do you want to book?' => 'tomorrow'
    ],
    [
        'Timestamp' => '2018-03-01',
        'What\'s your name?' => 'Johnny',
        'When do you want to book?' => 'tomorrow'
    ],
];

// get the headers
$headers = array_keys(array_values($data)[0]);

// open the file
$resource = fopen('output.csv', 'w');

// put the headers
fputcsv($resource, $headers);

// put the data
foreach ($data as $d) {
    fputcsv($resource, $d);
}

// close the file
fclose($resource);