Mobile Detection and cURL redirect giving 404 - php

Question

So I have a desktop (www.example.com/friends.php) and separate mobile site (m.example.com/friends.php). Not all pages on the desktop site exist on the mobile site.
The Goal: I am detecting a mobile device, then if it proves true, I want to capture the desktop URL after the .com (friends.php), and substitute the mobile domain "m.example.com + $pagename". I then want to detect if the page exists on the mobile domain via cURL (see below). If it exists, I want it to redirect to the corresponding mobile page, if it doesn't exists (returns 404), it should redirect to the base mobile domain.
I currently have the function set to alert if a mobile page is found or not based on the 404.
The issue: when I testa page I know does not exist, it alerts "mobile page found" always, and then will redirect to the mobile site 404 page. What am I missing here? I've stared at this for hours.
The Code:
function isMobile() {
return preg_match("/(android|avantgo|blackberry|bolt|boost|cricket|docomo|fone|hiptop|mini|mobi|palm|phone|pie|tablet|up\.browser|up\.link|webos|wos)/i", $_SERVER["HTTP_USER_AGENT"]);}
if(isMobile()){
function curPageName() {
return substr($_SERVER["SCRIPT_NAME"],strrpos($_SERVER["SCRIPT_NAME"],"/")+1);
}
$pagename = curPageName();
$mobileurl = 'http://m.example.com/' + $pagename;
$curl = curl_init($mobileurl);
curl_setopt($curl, CURLOPT_NOBODY, true);
$result = curl_exec($curl);
if ($result !== false) {
$statusCode = curl_getinfo($curl, CURLINFO_HTTP_CODE);
if ($statusCode == 404) {
echo "<script type='text/javascript'>alert('mobile url not found');</script>";
header("Location: http://m.example.com/");
} else {
echo "<script type='text/javascript'>alert('mobile url found');</script>";
header("Location:" + $mobileurl);}
} else {
echo "<script type='text/javascript'>alert('mobile url not found');</script>";
header("Location: http://m.example.com/");
}
} else {
return false;
}