Quick (unfinished) script that I run on my PI at home to check sites are up.

check website is up.php

<?php

date_default_timezone_set('Europe/London');

function sendmail($site,$contacts,$name,$date)
{
        $to      = $contacts;
        $subject = 'Alert ' . $site . ' appears to be down - ' . $name;
        $message = $site . ' is down, please check now ' .$date;
        $headers = 'From: donotreply@depicus.com (Depicus Site Monitor)' . "\r\n" .
            'Reply-To: donotreply@depicus.com (Do Not Reply)' . "\r\n" .
            'X-Mailer: PHP/' . phpversion();
        mail($to, $subject, $message, $headers);
}

function curlsite($site,$contacts,$name,$date)
{
        $ch = curl_init();
        curl_setopt($ch, CURLOPT_URL, "http://" . $site . "/");
        curl_setopt($ch, CURLOPT_HEADER, true);
        curl_setopt($ch, CURLOPT_NOBODY, true);
        curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
        curl_setopt($ch, CURLOPT_FOLLOWLOCATION, false);
        curl_setopt($ch, CURLOPT_MAXREDIRS, 2); //follow up to 2 redirections - avoids loops
        $data = curl_exec($ch);
        curl_close($ch);
       if (!$data) {
                echo "Domain could not be found " . $site . "<br />";
                sendmail($site, $contacts,'Domain not found',$date);
                return;
        }
        else {
                preg_match_all("/HTTP\/1\.[1|0]\s(\d{3})/",$data,$matches);
                $code = end($matches[1]);
                if ($code == 200) {
                //echo "Page Found " . $site . "<br />";
                //sendmail($site, $contacts);
                }
                elseif ($code == 404) {
                echo "Page Not Found " . $site . "<br />";

                sendmail($site, $contacts,$name,$date);
                return;
                }
        }
}

$sitestocheck = array( array( "site" => "www.depicus.com",
          "contact" => "me@example.com,you@example.com",
          "name" => "My Apple"
        ),
        array( "site" => "blog.depicus.com",
          "contact" => "me@gmail.com",
          "name" => "View All Oranges",
        ),
        array( "site" => "t.depicus.com",
          "contact" => "you@hotmail.com",
          "name" => "View All Oranges",
        )
 );

foreach ($sitestocheck as $i => $row)
{
        $date = date('m/d/Y h:i:s a', time());
        curlsite($row['site'],$row['contact'],$row['name'],$date);
}

?>