<?php
$email = $_POST['Email_Address'];
$full_name = $_POST['Full_Name'];
$entry = $full_name;
$entry .= ",";
$entry .= $email;
$file = fopen("contacts.csv","w");
fputcsv($file,explode(',',$entry));
fclose($file);
?>

<form method="post" action="php-forms/subscribeform.php">
<input placeholder="Name" type="text" name="Full_Name" id="Full_Name" required />
<input placeholder="Email" type="email" name="Email_Address" id="Email_Address" required />
<input class="formBtn" type="submit" />
<input class="formBtn" type="reset" />
</form>