The code below is a attempt to create a persistent login cookie. I am an amateur and not professional so this is the first attempt to have secure remember me cookie. Now I want you guys to review two things:I am trying to create a system like best way to implement remember me but I am not sure if I have done the same thing as explained there ( username row in table and cookie value isn't there but i have added).Is my code a good way to secure remember me cookie ? Any other suggestions or critiques are welcome.    if (isset($_POST['rememberme'])) {    $hash = sometext;    $identifier = md5($username);    $token = hash('sha512',$hash);    setcookie('auth', $username. , .$identifier. , . $token, time()+31556926);    $query=$db->prepare(SELECT username from tokens WHERE username=:username);    $query->execute(array(':username'=>$username));    if($query->rowCount() <=0 ){    $result = $db->prepare(INSERT INTO tokens (username,identifier,token) VALUES (:username,:identifier,:token));    $result->execute(array(':username'=>$username,':identifier'=>$identifier,':token'=>$token));     }    }    if(isset($_COOKIE[auth])){    $pieces = explode(,, $_COOKIE[username]);    $username = $pieces[0];    $Uidentifier = $pieces[1];    $Utoken = $pieces[2];    $sql=$db->prepare(SELECT * FROM tokens WHERE identifier=:identifier);    $sql->execute(array(':identifier'=>$Uidentifier));    if($sql->rowCount()>0){     $row = $sql->fetch(PDO::FETCH_ASSOC);     $dbtoken = $row['token'];     if($Utoken==$dbtoken){     $newhash = 'sometext';     $newtoken = hash('sha512',$newhash);     $que=$db->prepare(UPDATE tokens SET token=:token WHERE identifier=:identifier);     $que->execute(array(':token'=>$newtoken,':identifier'=>$Uidentifier));     setcookie('auth', $username. , .$identifier. , . $token, time()+31556926);     header(Location:home.php);     }     if($Utoken!=$dbtoken){     echo Unauthorized login attempt!;     setcookie(auth,,time()-31556926);     $stmt->$db=(DELETE FROM tokens WHERE identifier=:identifier);     $stmt->execute(array(':identifier'=>$identifier));     header(Location:login.php);      }     }    } 
Persistent login (remember me cookie) using PHP
php;beginner;sql;session