PHP $_Post variables print but still give index errors?

Question

Hey, I've got what has become an extremely frustrating problem with $_Post variables. I'll give examples of code rather than the actual segments to save time and confusion. On one page I'm doing this:

<? echo "<form name='form' action='page.php' method='post'>
         <input type='hidden' name='slot' value=".$i.">
         </form>";
?>

The $i is an index in a while loop (I'm echoing this simple form several times). The form itself is submitted with a bit a javascript.

All's well at this point, the form is submitted properly and takes me to another page, where I need to use that "slot" value to do some other junk. However, when I try to do this:

<? echo "<form name='another_form' action='another_page.php' method='post'>
         <input type='hidden' name='slot_num' value=".$_POST['slot'].">
         //SOME OTHER HIDDEN VARS
         </form>";
?>

or this...

<? echo "<form name='another_form' action='another_page.php' method='post'>
         <input type='hidden' name='slot_num' value=";
         echo $_POST['slot'];
          echo ">
         //SOME OTHER HIDDEN VARS
         </form>";
?>

or this...

<? //TOP OF PAGE
$slots = $_POST['slot'];
?>

<? //FURTHER DOWN
<? echo "<form name='another_form' action='another_page.php' method='post'>
     <input type='hidden' name='slot_num' value=".$slots.">
     //SOME OTHER HIDDEN VARS
     </form>";
?>

...all I get is an Undefined index: slot etc.. etc... error, and source of the php document just has blank space. Funny thing is, if I simply do this:

echo $_POST['slot'];

at the top of the page, it prints out the value from the previous page just fine, however, if I view the source, it still shows an Undefined index error instead of the value. I KNOW the value is getting passed because it prints, but I can't use it for anything else because if I try to include it in my php code, it just displays an error and gives a blank value!

I've also tried using $HTTP_POST_VARS['slots'] with the same result... I am at wits end after several hours of experimentation... any advice?

Answer 1

check for emptiness:

if(empty($_POST['foo'])) {
  $foo = "default foo";
} else {
  $foo = $_POST['foo'];
}

print "My foo is '$foo'";

Answer 2

Well I can't see anything wrong apart from a few syntax problems... okay so first of all, can you post me your javascript so I can see that.

Now instead of what you are doing with that, try this code:

?> <form name="another_form" action="another_page.php" method="post">
         <input type="hidden" name="slot_num" value="<?php echo isset($_REQUEST['slot'])?$_REQUEST['slot']:'not found'; ?>">
         </form>
<?

I am not fully sure what is wrong but i don't think the problem is in the code you've posted. it's probably sitting elsewhere so keep sending through code.

Answer 3

Edit:

Based on your comments and posted code, you seem to be trying to echo $_POST['slot'] when you should be echoing $_POST['slots']... note the s at the end.

---

Since $_POST is a super global, it is available anywhere on your page, so your code should work.

I noticed that you mixed slot and slots as the index in you post (you wrote $HTTP_POST_VARS['slots'] as the last example and $_POST['slot'] everywhere else). Could that be the reason?

To check what $_POST looks like, try this right about where you want to print the hidden value (though it should work the same anywhere on your page):

<?php
echo "<pre>";
print_r($_POST);
echo "</pre>";
?>

Also, your slot isn't being echoed with quote marks around it, so it should be:

<?php echo "<form name='another_form' action='another_page.php' method='post'>
         <input type='hidden' name='slot_num' value='".$_POST['slots']."'>
         //SOME OTHER HIDDEN VARS
         </form>";
?>

Answer 4

Try replacing...

<? //TOP OF PAGE
$slots = $_POST['slot'];
?>

with..

<?php //TOP OF PAGE
isset($_POST['slot']) : $slots = $_POST['slot'] ? $slots = '';
?>

Best of luck, hope that helps!