Move to next page automatically when contor hits specific value - php

Question

I am trying to build up a script that sends emails to users and pauses 1 hour after x number of emails. But I get 'Page is not redirecting properly', despite the fact when I access the query string manually it works:
cron-wordpress.php?page=1 // works manually
cron-wordpress.php?page=2 // works manually
cron-wordpress.php?page=3 // works manually
Here is the meat of the script:
EDIT SIMPLIFIED THE PROBLEM
cron-wordpress.php
$page = isset($_GET['page']) ? $_GET['page'] : 0;
$divide = 10;
$start = $divide*$page;
$emails = array();
for ($i = 0; $i <= 300; $i++) { // 300 emails in the dbs that means 30 pages $divide = 10
array_push($emails, $i.'#email.com');
}
$emails = array_slice($emails, $start, $divide);
$url = "http://".$_SERVER['SERVER_NAME'].'/wordpress/blog/cron_test.php';
$count = 0;
foreach ($emails as $email) {
echo 'Mail send to '.$email.'<br>';
$count++;
if (($count % $divide == 0) !== false && $count < 2000) {
sleep(2);
$page_nr = $count/$divide + 1;
header('Location: '.$url.'?page='.$page_nr);
//die();
//exit;
}
}