$login = 'Админ';  
    $password = '123456'; 

<form action="reg.php" method="post">  
<p>Логин </p><input name="user_login" type="text" /><br>  
<p>Пароль </p><input name="user_password" type="password" /><br>  
<input name="aaa" type="submit" value="Вход" />  
</form>

if($login === $user_login && $password === $user_password) 

<form action="reg.php" method="post">  
<p>Логин </p><input name="user_login" type="text"><br>  
<p>Пароль </p><input name="user_password" type="password"><br>  
<input name="aaa" type="submit" value="Вход">  
</form>

<?php 
    $user_login = !empty($_POST['user_login'])?$_POST['user_login']:NULL;  
    $user_password = !empty($_POST['user_password'])?$_POST['user_password']:NULL; 
        
    $login = 'Админ';  
    $password = '123456'; 

    if($login == $user_login && $password == $user_password)  
        header("Location: reg2.php");
    else  
        echo 'bad';  
?>  

<?php 
    $user_login = !empty($_POST['user_login'])?$_POST['user_login']:NULL;  
    $user_password = !empty($_POST['user_password'])?$_POST['user_password']:NULL; 
        
    $login = 'Админ';  
    $password = '123456'; 
    if($login == $user_login && $password == $user_password)  
        echo 'Пункт назначения :)';  
    else  
        header("Location: reg.php");
?>  

<?php 
    $user_login = !empty($_POST['user_login'])?$_POST['user_login']:NULL;  
    $user_password = !empty($_POST['user_password'])?$_POST['user_password']:NULL; 
        
    $login = 'Админ';  
    $password = '123456'; 
    if($login == $user_login && $password == $user_password)  
        header("Location: reg2.php");
    else  
        header("Location: reg.php");
?>  

<?php 
    $user_login = !empty($_POST['user_login'])?$_POST['user_login']:NULL;  
    $user_password = !empty($_POST['user_password'])?$_POST['user_password']:NULL; 
        
    $login = 'Админ';  
    $password = '123456'; 

    if($login == $user_login && $password == $user_password)  
        header("Location: reg2.php");
    else  
        echo 'Что-то не так<br>';  
		print_r($login);
		print '<br>';
		print_r($password);
?>

  $user_login = !empty($_POST['user_login'])?$_POST['user_login']:NULL;  
    $user_password = !empty($_POST['user_password'])?$_POST['user_password']:NULL; 
        
    $login = 'Админ';  
    $password = '123456'; 

$login = 'Админ';  
$password = '123456'; 

  print_r($login);
		print '<br>';
		print_r($password);

fwrite($handle, time() . '|' . $username . '|' . $text);

date('d-m-Y H:i:s', $time);

error_reporting(E_ALL);

Warning: set_time_limit() has been disabled for security reasons in /home/u011867260/public_html/index.php on line 4