Wont proceed if enter the correct uname and pass. After I uploaded the code online. It shows no error at all. The code works smoothly in offline [duplicate]

<?php
class DBConnection{

    private $host = 'localhost';
    private $username = 'id17280929';
    private $password = 'EpidemicResearch12345*';
    private $database = 'id17280929';
    
    public $conn;
    
    public function __construct(){

        if (!isset($this->conn)) {
            
            $this->conn = new mysqli($this->host, $this->username, $this->password, $this->database);
            
            if (!$this->conn) {
                echo 'Cannot connect to database server';
                exit;
            }            
        }    
        
    }
    public function __destruct(){
        $this->conn->close();
    }
}
?>

This is the Db connection File

    <?php
    session_start();
    $dev_data = array('id'=>'-1','firstname'=>'Developer','lastname'=>'','username'=>'admin','password'=>'5da283a2d990e8d8512cf967df5bc0d0','last_login'=>'','date_updated'=>'','date_added'=>'');
    if(!defined('base_url')) define('base_url','https://mywebsitelink.000webhostapp.com/');
    if(!defined('base_app')) define('base_app', str_replace('\','/',__DIR__).'/' );
    if(!defined('dev_data')) define('dev_data',$dev_data);
    require_once('classes/DBConnection.php');
    require_once('classes/SystemSettings.php');
    $db = new DBConnection;
    $conn = $db->conn;
    
    function redirect($url=''){
        if(!empty($url))
        echo '<script>location.href="'.base_url .$url.'"</script>';
    }
    function validate_image($file){
        if(!empty($file)){
            if(@getimagesize(base_url.$file)){
                return base_url.$file;
            }else{
                return base_url.'dist/img/no-image-available.png';
            }
        }else{
            return base_url.'dist/img/no-image-available.png';
        }
    }

This the config.php File

My Problem is if enter the correct info nothing happens to the login form. If i enter the incorrect info, the says incorrect, which is correct. I can’t explain any further. I hope you understand what I am pointing about. Thanks for your help.