login problems

[kows]

I only said that you could not send headers after you've sent output to the browser. every time you echo or print something, or display HTML, you're sending output to the browser. if you wish to send cookies on a page, your logic for deciding whether or not these cookies should be set (or destroyed) must be done before you send any output to the browser. in your logout script, for example, you start outputting your HTML and then you try to destroy your cookies by calling setcookie() with a time stamp in the past -- normally, this would throw some sort of error that told you that you could not send headers after output is sent ...

... and then, I realized you were using output buffering (ob_start()). I would firmly suggest against using output buffering unless you actually have a reason to use it (which you don't in this case). it promotes improper coding by letting you get away with certain things (and that may seem like it makes things convenient for you, but I would argue against that). properly written and formatted scripts will be easier to maintain in the future -- in this case, properly written/formatted would mean that the majority of your login/logout logic should happen at the beginning of all of your scripts (which is what I mentioned before and above).

so, to answer your question -- headers can be called within IF statements, yes.

but, there are still other issues with your script that I've discussed in my previous post; for example, this snippet of code from index.php:

            setcookie(ID_my_site, $_POST['username'], $hour);
            setcookie(Key_my_site, $_POST['pass'], $hour);
            if($_POST["admin"]=="yes"){
                setcookie(Admin_my_site, $_POST['admin'], $hour);
                print("<span style=\"float: left; text-align: left; padding: 5px 5px 5px 5px;\">Welcome ".$myusername."! <br />Visit your <a style=\"text-decoration: none;\" onmouseover=\"this.style.textDecoration='underline';\" onmouseout=\"this.style.textDecoration='none';\" href=\"login/member.php\">member's stat</a> <br /><a style=\"text-decoration: none;\" href=\"login/logout.php\" onmouseover=\"this.style.textDecoration='underline';\" onmouseout=\"this.style.textDecoration='none';\" >Logout</a></span>");
            }else{
                setcookie(User_my_site, $_POST['admin'], $hour);
                print("<span style=\"float: left; text-align: left; padding: 5px 5px 5px 5px;\">Welcome <span id=\"myusername\">".$myusername."</span>! <br />Visit your <a style=\"text-decoration: none;\" href=\"login/member.php\" onmouseover=\"this.style.textDecoration='underline';\" onmouseout=\"this.style.textDecoration='none';\" >member's stat</a> <br /><a style=\"text-decoration: none;\" href=\"login/logout.php\" onmouseover=\"this.style.textDecoration='underline';\" onmouseout=\"this.style.textDecoration='none';\" >Logout</a></span>");
            } 

ignoring the horrendous HTML (you shouldn't use echo/print to emit HTML), you're calling setcookie() four times and you're using constants to define the names of these cookies. however, the constants don't exist (and I'm not even sure you know what a constant is) and when PHP looks for these constants they will be null, which means you're setting cookies with null names. this means there is no possible way for you to reference them, so that isn't very helpful. briefly, here is the extremely simple difference between how to call or use constants, variables, strings, and functions:

CONSTANT

$variable

"string"

'string'

function()

so, in your code, you can see that you're trying to use a constant to define a cookie name (ID_my_site), but you need to use strings:

setcookie("my_cookie_name", "my_cookie_value", time() + 3600); 

then, I could reference $_COOKIE['my_cookie_name'] to get the value "my_cookie_value" after a full reload of the current page (cookies don't take affect until you've loaded a new page).

and then, there's the thing I mentioned about sessions. sessions would be better than cookies in your case (in my opinion) simply because you're setting a cookie for just an hour. cookies are generally used to store long term information -- not short term. sessions will persist for up to 20 minutes by default and will store any data on the server rather than the client (which is good for information that may need a bit more security), and a user doesn't need anything enabled in their browser to make sessions work. I would suggest that you read up on them here through the simple example.

however, as a final note, if you are not really understanding PHP and this tutorial/script is your first step into it, I would highly suggest you take a step back and look into some beginner tutorials -- perhaps the ones from W3Schools would be a good start.

and don't be afraid to ask questions if you don't understand anything I just wrote!