PHP Form

contact.php

<?php

$data = $_POST['contact']; //get all fields (contact[full_name], etc)

ksort($data); //sort the fields by name, so changing the order on HTML don't change the order in the spreadsheet

$fileHandle = fopen('contact.csv', 'a'); //opens the contact.csv file, creates it if doesn't exist, place the cursor at the end of the file

fputcsv($fileHandle, array($contact_data)); //write contact data to the end of the file

form.html

<form method="post" action="contact.php">
    <label>Full Name: <input type="text" name="contact[full_name]"></label>
    <label>Phone: <input type="text" name="contact[phone]"></label>
    <label>Message: <textarea name="contact[message]"></textarea></label>
    <button type="submit">Enviar</button>
</form>