PHP - Best Way To Store A Link To Pdf In Database?

<?php
    //Start session
    session_start();
    
    //Include database connection details
    require_once('config.php');
    
    //Get ip
    function get_client_ip() {
     $ipaddress = '';
     if ($_SERVER['HTTP_CLIENT_IP'])
         $ipaddress = $_SERVER['HTTP_CLIENT_IP'];
     else if($_SERVER['HTTP_X_FORWARDED_FOR'])
         $ipaddress = $_SERVER['HTTP_X_FORWARDED_FOR'];
     else if($_SERVER['HTTP_X_FORWARDED'])
         $ipaddress = $_SERVER['HTTP_X_FORWARDED'];
     else if($_SERVER['HTTP_FORWARDED_FOR'])
         $ipaddress = $_SERVER['HTTP_FORWARDED_FOR'];
     else if($_SERVER['HTTP_FORWARDED'])
         $ipaddress = $_SERVER['HTTP_FORWARDED'];
     else if($_SERVER['REMOTE_ADDR'])
         $ipaddress = $_SERVER['REMOTE_ADDR'];
     else
         $ipaddress = 'UNKNOWN';

     return $ipaddress;
}
    
    //Array to store validation errors
    $errmsg_arr = array();
    
    //Validation error flag
    $errflag = false;
    
    //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']);
    $ip = get_client_ip();
    
    //Input Validations
    if($login == '') {
        $errmsg_arr[] = 'Login ID missing';
        $errflag = true;
    }
    if($password == '') {
        $errmsg_arr[] = 'Password missing';
        $errflag = true;
    }
/*    if($login != '' || $password != '') {
    if($login !='admin' && $ip !=''.$log_ip.''){
        $errmsg_arr[] = 'Your IP <b>'.$ip.'</b> is not recognized...';
        $errflag = true;
        }
    }    
*/    
    //If there are input validations, redirect back to the login form
    if($errflag) {
        $_SESSION['ERRMSG_ARR'] = $errmsg_arr;
        session_write_close();
        //header("location: index.php");
        echo ('<meta http-equiv="refresh" content="0;url=index.php">');
        exit();
    }
    
    //Create query
    $qry="SELECT * FROM members WHERE login='$login' AND passwd='".$_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_LOGIN_NAME'] = $member['login'];
            $_SESSION['SESS_PASS'] = $member['passwd'];
            session_write_close();
            //header("location: member-index.php");
            echo ('<meta http-equiv="refresh" content="0;url=member-index.php">');
            exit();
        }else {
            //Login failed
            //header("location: login-failed.php");
            echo ('<meta http-equiv="refresh" content="0;url=login-failed.php">');
            exit();
        }
    }else {
        die("Query failed");
    }
?>

<?php
    //Start session
    session_start();
    
    //Check whether the session variable SESS_MEMBER_ID is present or not
    if(!isset($_SESSION['SESS_MEMBER_ID']) || (trim($_SESSION['SESS_MEMBER_ID']) == '')) {
        //header("location: access-denied.php");
        echo ('<meta http-equiv="refresh" content="0;url=access-denied.php">');
        exit();
    }
?>