<?php
$name = $_POST['name'];
$email = $_POST['email'];
$date = $_POST['date'];
$destination = $_POST['destination'];
$msg = $_POST['msg'];

//TODO the file write here VV, use 'a' instead of 'w' too ADD to the file instead of REWRITING IT.
$arr = [$name,$email,$date,$destination,$msg];

$write = json_encode($arr);
echo $write;

$file = fopen('data.txt', 'a');
fwrite($file, $write);
fclose($file);
// echo $arr[];
 ?>

["Simon","example@example.com","0101-01-01T01:01","Ohio","Message here"][null,null,null,null,null]

<?php
if (isset($_POST['name'])
        && isset($_POST['email'])
        && isset($_POST['date'])
        && isset($_POST['destination'])
        && isset($_POST['msg'])) {
    $name = $_POST['name'];
    $email = $_POST['email'];
    $date = $_POST['date'];
    $destination = $_POST['destination'];
    $msg = $_POST['msg'];

    //TODO the file write here VV, use 'a' instead of 'w' too ADD to the file instead of REWRITING IT.
    $arr = [$name,$email,$date,$destination,$msg];

    $write = json_encode($arr);
    var_dump( $write);
    $file = fopen('data.txt', 'a');
    fwrite($file, $write);
    fclose($file);
    // echo $arr[];
}
?>