Undefined index: do in - php

Question

I am trying to install a arcade script and keep getting these errors, can anyone help out?
Notice: Undefined index: do in C:\xampp\htdocs\meggiemoos\arcade\install\new.php on line 34
Notice: Use of undefined constant sql - assumed 'sql' in C:\xampp\htdocs\meggiemoos\arcade\install\new.php on line 34
Notice: Undefined index: do in C:\xampp\htdocs\meggiemoos\arcade\install\new.php on line 37
Notice: Use of undefined constant sql2 - assumed 'sql2' in C:\xampp\htdocs\meggiemoos\arcade\install\new.php on line 37
This is line 34 to 38
<? if ($_GET['do'] == sql) {
include ('sql1.php');
}
else if ($_GET['do'] == sql2) {
include ('sql2.php');
I have tried if isset($_GET but I might have done it wrong as of the closed bracket { for next line, I was told to add another bracket as well but never told where.
Thanks for your help :)

Answer 1

Try
if (isset($_GET['do']) && $_GET['do'] == 'sql')

Answer 2

sql by itself is nothing to PHP. You need to have it as a string or variable, as follows:
<? if ($_GET['do'] == "sql") {
or
$var = "sql";
<? if ($_GET['do'] == $var) {
As for the line 37 error, the server cannot find the GET variable named 'do', so you need to find out why it's not being set. You might consider adding this to earlier parts of your script:
if (!isset($_GET['do'])) {
exit("do variable was not set!");
}
else {
$do = $_GET['do'];
}
That way, you don't have to keep typing $_GET['do'], which can get tedious.