How to use mysql_num_rows to check if username has been used?

I think I'm missing something simple on the code below, but I can't find the problem.  This is for a registration form and I'm just trying to query the table (users) and see if the username has already been used.  If the username has already been taken then tell the user, if the username hasn't been taken register the user.  What am I missing here?
// check the username and make sure it hasn't been taken
$result = mysql_query ("SELECT username from users WHERE username = '$new_user_name'");
$num_rows = mysql_num_rows($result);
 
if ($num_rows = '1') {
	echo "That username is already in use, please select another username! <a href='add_user.php'>Try Again</a>";
}
if ($num_rows = '0') {
		 mysql_query ("INSERT INTO users (first_name, last_name, username, password, email, state_id, state)
		 VALUES ('$first_name', '$last_name', '$user_name', '$encrypted_password', '$email', '$state_id', '$state_name')");	
         echo 'Good news, the user was added!';
      }

Open in new window

jbpeakeAsked:
Who is Participating?
I wear a lot of hats...

"The solutions and answers provided on Experts Exchange have been extremely helpful to me over the last few years. I wear a lot of hats - Developer, Database Administrator, Help Desk, etc., so I know a lot of things but not a lot about one thing. Experts Exchange gives me answers from people who do know a lot about one thing, in a easy to use platform." -Todd S.

BrianMMCommented:
Is it doing anything?

try:
// check the username and make sure it hasn't been taken
$result = mysql_query ("SELECT username from users WHERE username = '$new_user_name'");
 
if($result) {
	if(mysql_num_rows($result) > 0) {
		echo "That username is already in use, please select another username! <a href='add_user.php'>Try Again</a>";
	} else {
		// Insert...
		mysql_query ("INSERT INTO users (first_name, last_name, username, password, email, state_id, state)
                 VALUES ('$first_name', '$last_name', '$user_name', '$encrypted_password', '$email', '$state_id', '$state_name')");     
		echo 'Good news, the user was added!';
	}
} else {
	echo "Sorry problem with query:".mysql_error();
}

Open in new window

0
OpalelementCommented:
I would agree with the "if($var > 0) else" method, as it means there will always be a Yes or No result, even if there happens to be more than 1.

However, in your code I am guessing you always got both?

The problem is with these:
if ($num_rows = '1')
if ($num_rows = '0')

You need another = sign in both of those, like this:
if ($num_rows == '1')
if ($num_rows == '0')

From http://www.php5-tutorial.com/basics/if-statements/
As you can see, we are using two equal signs after each other - why is that? In PHP, and in many other programming languages, a single equal sign is an assignment operator. It's used to assign a value to e.g. a variable. Two equal signs are a comparison operator, that is, it's used to compare two values. So, in this case, we use two equal signs to compare the two items: $number and 42. Had we only used one equal sign, 42 would be assigned to $number, and no comparison would have been made.
0

Experts Exchange Solution brought to you by

Your issues matter to us.

Facing a tech roadblock? Get the help and guidance you need from experienced professionals who care. Ask your question anytime, anywhere, with no hassle.

Start your 7-day free trial
BrianMMCommented:
yes... that is correct also... should have spotted that in original code :)

General practice of using if(mysql_num_rows($result) > 0) is 'safer' incase for any reason there is more than one.
0
It's more than this solution.Get answers and train to solve all your tech problems - anytime, anywhere.Try it for free Edge Out The Competitionfor your dream job with proven skills and certifications.Get started today Stand Outas the employee with proven skills.Start learning today for free Move Your Career Forwardwith certification training in the latest technologies.Start your trial today
Scripting Languages

From novice to tech pro — start learning today.