PHP adduser到ubuntu没有设置正确的主目录？

i have this PHP code

<?php
error_reporting(E_ALL);
ini_set('display_errors', TRUE);
ini_set('display_startup_errors', TRUE);



if(!empty($_GET) && !empty($_GET['user']) && !empty($_GET['mem']) && !empty($_GET['id']) &&!empty($_GET['k'])) {
    $user = $_GET['user'];
    $mem = $_GET['mem'];
    $id = $_GET['id'];
    $pass = $_GET['k'];
    $name =  $user."-".$id;
    $directory = "/home/servers/".$name;
    $salt = dechex(mt_rand(0, 2147483647)) . dechex(mt_rand(0, 2147483647)); 

    echo "User: ".$user; 
    echo "<br/>";
    echo "Memory: ".$mem;
    echo "<br/>";
    echo "ID: ".$id; 
    echo "<br/>";
    echo "Pass: ".$pass;
    echo "<br/>";
    echo "Directory: ".$directory;
    echo "<br/>";
    echo "<br/>";
    echo "name: ".$name;
    echo "<br/>";

    if (!file_exists($directory)) {
        mkdir($directory, 0, true);
    }
    else {
        echo "Dir already exists?";
    }
    $outputuser = shell_exec("sudo useradd -s /bin/false -d ".escapeshellarg($directory)." -p ".crypt($pass,$salt)." ".escapeshellarg($servername));

}


?>

now when i run the page i get this output

User: trotski94
Memory: 1024
ID: 1
Pass: test
Directory: /home/servers/trotski94-1

name: trotski94-1
Dir already exists?

which is expected. but when i go to login on the ubuntu machine it says there is no home directory, using / as home instead, why is the -d flag not setting the home directory?

check user directory by: cat /etc/passwd | grep trotski94

mayby escapeshellarg may spoil something