Mailchimp double_optin option not working - php

Question

I've followed this tutorial to implement mailchimp API v2.0 on my website.
It works great, however the double_optin option that I wanted to add and set to false (so that users don't need to validate their registration via e-mail) doesn't seem to be working. It's like if it was not taken into consideration at all, users still need to validate the registration via e-mail.
Is 'double_optin' => false placed at the wrong place? I had a look at mailchimp documentation but my level in programmation is not good enough to identify what is wrong.
Thanks for your help
<?php
$api_key = "12345486-us8";
$list_id = "123";
require('Mailchimp.php');
$Mailchimp = new Mailchimp( $api_key );
$Mailchimp_Lists = new Mailchimp_Lists( $Mailchimp );
$subscriber = $Mailchimp_Lists->subscribe( $list_id, array( 'email' => htmlentities($_POST['email']),'double_optin' => false ) );
if ( ! empty( $subscriber['leid'] ) ) {
echo "success";
}
else
{
echo "fail";
}
?>

Answer 1

According to this (admittedly unofficial-looking) Mailchip_Lists documentation, you'll want to pass FALSE as the 5th parameter to subscribe().
Example:
$double_optin = FALSE;
$subscriber = $Mailchimp_Lists->subscribe(
$list_id,
array('email' => htmlentities($_POST['email'])),
NULL, // merge_vars
'html', // email_type
$double_optin
);