[SOLVED] Question about returning values in functions

[limitphp]

I'm still a little wet behind the ears with functions.

I want to create a function that checks to see if a username is taken:

function does_username_exist($username)
{
$queryUsername = "SELECT username FROM user WHERE username = '$username'";
$result = mysql_query($queryUsername) or die (mysql_error());
$rowCount=mysql_affected_rows();	
if ($rowCount>0) {
	$usernameTaken = 1;
}else {
              $usernameTaken = 0;
        }
        return $usernameTaken ;

}

 

Is that the correct way to do it?

Do you have to return the value you inputted?

I input $username into the function, but I'm returning a different variable.  Is that ok?

Can you return multiple variables?

 

Is this the proper way to use the function?:

$usernameTaken = does_username_exist($username);

 

[.josh]

everything looks fine, except that mysql_affected_rows is only used for things that alter the table (insert, update, delete, etc...) You'll want to use mysql_num_rows instead

[rhodesa]

yeah, mysql_num_rows()...and also, don't bother with an extra variable...just return the 1 or 0 as soon as you know:

function does_username_exist($username)
{
   $queryUsername = "SELECT username FROM user WHERE username = '$username'";
   $result = mysql_query($queryUsername) or die (mysql_error());
   $rowCount=mysql_num_rows($result);
   if ($rowCount>0) {
      return 1;
   }
   return 0;
}

 

edit: for that matter...just force mysql_num_rows to a boolean:

function does_username_exist($username)
{
   $queryUsername = "SELECT username FROM user WHERE username = '$username'";
   $result = mysql_query($queryUsername) or die (mysql_error());
   return (boolean) mysql_num_rows($result);
}

[.josh]

Do you have to return the value you inputted?

No. You don't have to return anything at all.

 

I input $username into the function, but I'm returning a different variable.  Is that ok?

Yes. 

 

Can you return multiple variables?

No, not individually.  But you can return an array.

[limitphp]

Awesome, thanks for the info guys!

 

this looks great and more simplified:

function does_username_exist($username)
{
   $queryUsername = "SELECT username FROM user WHERE username = '$username'";
   $result = mysql_query($queryUsername) or die (mysql_error());
   return (boolean) mysql_num_rows($result);
}

[rhodesa]

Awesome, thanks for the info guys!

 

this looks great and more simplified:

function does_username_exist($username)
{
   $queryUsername = "SELECT username FROM user WHERE username = '$username'";
   $result = mysql_query($queryUsername) or die (mysql_error());
   return (boolean) mysql_num_rows($result);
}

 

actually...one more edit...to protect from SQL Injection:

function does_username_exist($username)
{
   $queryUsername = sprintf("SELECT username FROM user WHERE username = '%s'",mysql_real_escape_string($username));
   $result = mysql_query($queryUsername) or die (mysql_error());
   return (boolean) mysql_num_rows($result);
}

[limitphp]

Awesome, thanks for the info guys!

 

this looks great and more simplified:

function does_username_exist($username)
{
   $queryUsername = "SELECT username FROM user WHERE username = '$username'";
   $result = mysql_query($queryUsername) or die (mysql_error());
   return (boolean) mysql_num_rows($result);
}

 

actually...one more edit...to protect from SQL Injection:

function does_username_exist($username)
{
   $queryUsername = sprintf("SELECT username FROM user WHERE username = '%s'",mysql_real_escape_string($username));
   $result = mysql_query($queryUsername) or die (mysql_error());
   return (boolean) mysql_num_rows($result);
}

 

Actually my $username already goes through:

$username = check_input($_POST['username']);

function check_input($value)
{
// Stripslashes
if (get_magic_quotes_gpc())
  {
  $value = stripslashes($value);
  }
  $value = mysql_real_escape_string($value);		  
return $value;
}

 

Which I learned from you guys as well.

[rhodesa]

awesome