Is my return written correctly for this type of connection?

Is my return written correctly for this type of connection?

My return is not returning back anything when attempting to find a
username, the sql is able to connect. Here is my code:
function usernameExists($username) {
global $conn;
$sql = "SELECT active FROM user
WHERE username='" . fixstr($username) . "' LIMIT 1";
if(returns_result($sql) > 0) {
return true;
} else {
return false;
}
}
Here is my connection:
/* Create a new mysql connect object with database connection parameters */
$conn = mysql_connect(db_server, db_user, db_pass);
if (!$conn)
die("Could not connect: " . mysql_error());
mysql_select_db(db_name, $conn);
My connection is not able to return anything but it does connect to the
server through fixstr.
Here is fixstr:
function fixstr($str){
$str = trim($str);
$str = str_replace("'", "''", $str);
return $str;
}
Why is my return not returning any results.