simple authentication using credentials in php

I need to write and authenticate user based on username, password and some other credentials like some of their user information name, mail etc. or some other thing. How can we do that in php?

My login code with username and password. how to add some credentials also with this program for authentication:

<?php

//Start session
session_start();

//Include database connection details
require_once('config.php');

//Array to store validation errors
$errmsg_arr = array();

//Validation error flag
$errflag = false;

//Connect to mysql server
$link = mysql_connect(DB_HOST, DB_USER, DB_PASSWORD);
if (!$link) {
    die('Failed to connect to server: ' . mysql_error());
}

//Select database
$db = mysql_select_db(DB_DATABASE);
if (!$db) {
    die("Unable to select database");
}

//Function to sanitize values received from the form. Prevents SQL injection
function clean($str)
{
    $str = @trim($str);
    if (get_magic_quotes_gpc()) {
        $str = stripslashes($str);
    }
    return mysql_real_escape_string($str);
}

//Sanitize the POST values
$login = clean($_POST['login']);
$password = clean($_POST['password']);

//Input Validations
if ($login == '') {
    $errmsg_arr[] = 'Login ID missing';
    $errflag = true;
}
if ($password == '') {
    $errmsg_arr[] = 'Password missing';
    $errflag = true;
}

//If there are input validations, redirect back to the login form
if ($errflag) {
    $_SESSION['ERRMSG_ARR'] = $errmsg_arr;
    session_write_close();
    header("location: login-form.php");
    exit();
}

//Create query
$qry = "SELECT * FROM members WHERE login='$login' AND passwd='" . md5($_POST['password']) . "'";
$result = mysql_query($qry);

//Check whether the query was successful or not
if ($result) {
    if (mysql_num_rows($result) == 1) {
        //Login Successful
        session_regenerate_id();
        $member = mysql_fetch_assoc($result);
        $_SESSION['SESS_MEMBER_ID'] = $member['member_id'];
        $_SESSION['SESS_FIRST_NAME'] = $member['firstname'];
        $_SESSION['SESS_LAST_NAME'] = $member['lastname'];
        session_write_close();
        header("location: member-index.php");
        exit();
    } else {
        //Login failed
        header("location: login-failed.php");
        exit();
    }
} else {
    die("Query failed");
}
?>

if that credentials in dynamic that will be good. How to do that?

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Link to original article：https://stackoverflow.com/questions/7459577/simple-authentication-using-credentials-in-php