检查$ _GET是否可用且具有特定值？

I'm trying to check to see if a $_GET value is available AND equal to 1 but the error is that the index is not defined.

<?php if ((isset($_GET['success'])) ||  ($_GET['success'] == 1)) { ?>
Do Something
<?php } ?>

Why is this a problem? I'm checking to see if it exists and then if it equals one and if so , do something.

Is there a better way to achieve this goal?

Change the || (OR) to && (AND)

if ((isset($_GET['success'])) &&  ($_GET['success'] == 1))

do this <?php if (isset($_GET['success']) { if($_GET['success']==1){} ?>

Do Something

<?php } ?>

You need to change the OR for an AND in the conditional (&&)

|| = OR

&& = AND, which is what should have been used.