Send multiple requests with multiple cookies (cURL + PHP)

Question

This issue comes from a situation that may look strange, but this purpose is fully intentional.

Here is the scenario : I have 3 scripts (let's call them A, B and C). Each one has to be executed every 5 seconds, with a specific cookie.

I wanted to automate the execution of these scripts with another one called "start.php", using cURL, which should set the proper cookie before executing any of those scripts.

Summary :

1. I call 'start.php' manually
2. start.php sets the cookie A, then calls A.php
3. Idem with B.php and C.php and proper cookies
4. Repeat every 5 seconds.

Here is what my script from start.php looks like :

   function startCrawling()
    {

    $currentChall = 1;
    $cookieValue = "";

    for ($currentChall = 0; $currentChall <= 3; $currentChall++) {

        $sql = getConnection()->prepare("SOME STUFF HERE");
        if ($sql->execute()) {
            while ($row = $sql->fetch(PDO::FETCH_ASSOC)) {
                if ($row['idChallenge'] == $currentChall) {
                    $cookieValue = $row['token'];
                    break;
                }
            }
        }

        sendRequest($currentChall, $cookieValue);
        sleep(1);
    }
}

    /**
    * Send the request to the given script
    */
    function sendRequest($id, $cookieValue)
    {
        $params = [
        'password' => 'p4ssw0rd'
    ];
    $defaults = array(
        CURLOPT_URL => 'http://localhost/script' . $id . '.php',
        CURLOPT_POST => true,
        CURLOPT_POSTFIELDS => $params,
        CURLOPT_HTTPHEADER => array("Cookie: AdminToken=".$cookieValue),

        CURLOPT_VERBOSE => true
    );
    $ch = curl_init();
    curl_setopt_array($ch, $defaults);

    $content = curl_exec($ch);
    curl_close($ch);

     if ($content === false) {
        echo 'Erreur Curl : ' . curl_error($ch);
     }
}

BUT, at the end, even if every script has been executed, the only value sent as a cookie is the PHPSSID (seen in my requestb.in). I have been searching workarrounds for 2 days, but I can't find any similar problem on the web.

Any help would be truly appreciated.

(Edited due to comments suggestion)