PHP Session variable is set, but PHP doesn't see it. Very strange.

Question

Okay, maybe this is because I've been coding for over 24 hours and my eyes are glazing over, but I'm stumped here. Why does this happen:

<?php
session_start();
$tmp = "index";

echo "A: " . $_SESSION['page_loaded']['index']; // returns 1
echo "B: " . $_SESSION['page_loaded'][$tmp]; // is set, but is empty
?>

I feel like I'm missing something very basic here but I don't know what.

Answer 1

Try it with the var_dump function to see it’s value.

Answer 2

Try using:

$tmp = 'index'; // Note the single quotes.
//...
echo "B: " . $_SESSION['page_loaded'][$tmp];

PHP interprets double and single quoted strings slightly differently. Read these articles here and here as that might be what you are facing.

UPDATE: Just to clarify (given the comments below) my reasoning to check if using single or double quoted strings are effecting the Original Posters problem is shown in the example below where the two strings are not equal:

$var = 1;

$tmpA = 'index_$var'; // will resolve to index_$var
$tmpB = "index_$var"; // will resolve to index_1

if ( $tmpA === $tmpB)
  echo 'Identical';
else
  echo 'Not Identical!'; // <--- we get this because they are NOT identical.

Answer 3

Where are you setting the following?

$_SESSION['page_loaded'][$tmp];

The following works:

<?php

    session_start();
    $tmp = "index";

    $_SESSION["page_loaded"][$tmp] = "Foo";

    echo "A: " . $_SESSION['page_loaded']["index"]; // foo
    echo "<br/>";
    echo "B: " . $_SESSION['page_loaded'][$tmp]; // foo

?>

Answer 4

you should use

 $_SESSION['page_loaded']['tmp'] = "index";

instead of

 $tmp = "index";

and to retrieve the value use this

  echo "B: " . $_SESSION['page_loaded']['tmp']; // the output is: B: index

(get rid of the dollar sign $)

Answer 5

I have a feeling you haven't actually cut and pasted that code? Is there anything you're leaving out?