1.Make a config file:
2.download rb.php file (https://github.com/yeriomin/redbean-single-file/blob/master/rb.php) or from official site.

config.php
----------------------

include"rb.php";
$username = "root";
$userpass = "";
$db = "shift";
$host = "localhost";
include "rb.php";
R::setup("mysql:host=$host;dbname=$db", "$username", "$userpass"); //for both mysql or mariaDB
R::ext('xdispense', function( $type ) {    return R::getRedBean()->dispense($type);});
R::freeze(true);
//R::debug(true) ; put it true if you want to debug your query


2.
include "config.php";
$signin=isset($_POST['signin'])?$_POST['signin']:"";
$username=isset($_POST['username'])?$_POST['username']:"";
$pw=isset($_POST['pw'])?$_POST['pw']:"";
if($username=="")
{
  $error="fill in username to sign in "
}
else if($pw=="")
{
  $error="fill in password to sign in "
}
else if($error=="")
{
$Query=R::getRow("SELECT pw FROM users WHERE username =:username",array(":username"=>$username));
if(count($Query)>0)
{
   if($pw===$Query["pw"])
    {
    print("Password match");
    //do what every you want here after password match
    }
}
else
{
echo $error;
}









R::freeze(true);