Returning value from a function.

[Anon]

I have a CheckPassword() function that I use on my site and wanted to add in a "user level" part to it. Now, I can get the user level out of db but I can't seem to access that "$level" variable outside the function. Any help on where the code is wrong would be helpful.

function CheckPassword($username, $password) {
global $level;
require("database_connect.lib");
//get their actual password
$query = "SELECT user_info.password FROM user_info WHERE (username = \"$username\")";
if ($result = mysql_query($query, $server_connect)) {
$row = mysql_fetch_row($result);
$checkpass = $row[0];
if ($password == $checkpass) {
//password is good
$l_query = "SELECT online.level FROM online WHERE (username =\"$username\")";
if($l_result = mysql_query($l_query, $server_connect)) {
$l_row = mysql_fetch_row($l_result);
$level = $l_row[0];
}
return true;
return $level;
}
else {
//password no good
print "<font colour = gold>Wrong password ($password) for $username.</font>";
}
}
else {
if(!$err_mess = mysql_error()) {
$err_mess = "Unknown error";
}
print "<font colour = gold>Unable to connect to database. Error : $err_mess.</font>";
}
}//end function
global $level;

As you can see from the above, I am validating they are who they say they are, then I am grabbing their "level" from the database. But I can't access $level outside the function. I thought global and return would help, but I couldn't get it to work.

Any help, as always, is much appreciated.

[Anon]

The problem with that function is you return twice, the first time you return from a function it "returns" that value to the caller.

Example, this will return 'true' and 'return $level' will be unreached code
return true;
return $level;

[Anon]

Okay...so I removed the return true line and went with just return $level and I still don't get the "$level" outside the function.

Any ideas?

Side note : I expected to get an error since I didn't return true. Is true assumed if not explicit?

[Anon]

If you return a value from a function, you need to set a variable equal to the function call... like so:

$my_level = CheckPassword($username, $userpass);

The value that you returned for $level in the CheckPassword function will now be stored in the $my_level variable.

By the way, it is almost always a bad idea to use "global" variables. Try starting a session and setting the level in a session variable with session_register(). If you need to change the value of multiple variables in a function, try passing the variables in by reference.

Good luck!

-Will

[Anon]

Thanks very much. But your comment of global = bad has piqued my interest. Can you elaborate as to why it is bad? I have only been programming about 2-3 years now and am learning the "finesse" now so I would like to hear why if possible.

[Anon]

Well, in PHP it's not as clear cut as in more structured languages. The general idea of global = bad is that you may be clobbering other instances of a variable with the same name. If access to a variable is required in an area of the program where said variable is out of scope, then the variable should be accessed via a pointer (not sure if this is possible in PHP...) or a pass by reference. If only one variable needs to be changed, then you can, of course, modify it using a return value.

I have not been programming PHP for very long. However, because of my background in strongly-typed languages, I tend to stay away from global variables. You can achieve the same effect by registering the variable in a session, and then you can always know exactly what variable you are accessing (by using session_is_registered(), etc). Even this is a bit too close to global variables for my comfort, but there really aren't other options unless you want to pass them via the address to the page (is that GET or POST method? I can never remember...), which tends to make things even more cluttered and confusing.

In addition, global variables tend to make code harder to follow, especially if someone else will be maintaining your code in the future.

Hopefully this was at least somewhat helpful... if my ramblings were completely incoherent, let me know and I'll try to post my thoughts a bit more concisely.

Cheers,
Will

[neuromancer]

No, return true returns the value of a constant named 'true'.

Outside your function, when your calling it do you assign level to the function?

$level=my_function(...)

[neuromancer]

Here are a few rules that I follow when writing functions

1, The function always returns a success or failure status of some kind, even if this is the diffrence between a signed and unsigned value (negitive numbers being errors and positive being descriptors for example)

2, Any data that I need to return (arrays, modified strings, etc) are accepted by refrence.

3, Function arguments are listed most to least important defaulting all values possible.

4, Functions should never refrence any external namespace ($GLOBALS) unless there is no other way around it

Example

function user_login($username,$password) {
if($username=='x' && $password=='y') {
return(true);
}
return(false)
}

function fetch_result_set($hstmt,&$result_set) {

populate result_set, return true or false

}

[Anon]

It's definitely good to be consistent when writing functions. As long as you document the code and maintain the same style throughout, you should be fine.
I prefer sometimes to have my functions return actual data, and they return an out-of-range piece of data on error (ex: returning negative on strlen()). The problem with this is that you end up having different error conditions to check for depending on the function; if they all return true or false, things are much cleaner.

Excellent suggestion, Neuro.

-Will