传递SESSION变量，出现错误

Question

I am trying to pass a session variable from one page to another but it seems liek the session variable is empty on the next page. Thanks for the help!

Here is the entirety of the code on the two pages.

mysql_connect($db_hostname, $db_username, $db_password);
mysql_select_db($db_sitename);
$pagename= $row_getDisplay['USER_NAME']; 
$query=mysql_query("SELECT * FROM COMMENTS WHERE COMMENT_ON='$pagename' LIMIT 0, $no_of_comments");
echo "<hr />";

echo "<h3>Latest Comments</h3>";
session_start();
$count = 0;
while($fetch=mysql_fetch_array($query)) 
{

  echo "<p>".$fetch['COMMENT']."<a href=delete_comment.php?count=".$count.">X</a><br/><sub><b>Comment by: </b>".$fetch['COMMENT_BY']."</sub><hr /><p>";
  $_SESSION[strval($count)]=$fetch['COMMENT'];
  //echo $_SESSION[strval($count)];
  $count = $count + 1;

  print_r($_SESSION);
}
mysql_close();

delete_comment.php

<?php
session_start();
print_r($_SESSION);
error_reporting(E_ALL);
ini_set('display_errors', '1');


$count = $_GET['count'];
echo $count;
$comment = $_SESSION[strval($count)];

$db_sitename="genydb";
$db_hostname="localhost";
$db_username=
$db_password=

$con = mysqli_connect($db_hostname, $db_username, $db_password, $db_sitename);

echo $comment;
$myquery = sprintf("DELETE FROM COMMENTS WHERE COMMENT=%s", GetSQLValueString($_SESSION[$_GET['count']], 'text'));
$mysql=($myquery) or die(mysql_error());

mysqli_close($con);

?>

This is the error

Notice: Undefined offset: 0 in /var/www/geny/bootstrap/delete_comment.php on line 8
$comment = $_SESSION[strval($count)];

Answer 1

I believe it is because you are using a numeric key with $_SESSION. I tried it out locally and I got this notice on the first page:

Notice: Unknown: Skipping numeric key 0 in Unknown on line 0

I saw this bug report as well after getting that notice https://bugs.php.net/bug.php?id=42472

If you do something like this it doesn't raise the notice and it passes the variable properly:

$_SESSION['keyName'][strval($count)]=$fetch['COMMENT'];

Edit: Thanks to Wiseguy for turning me on to this bit of info.

His comment below is:

According to this answer , "keys in the $_SESSION array are subject to the same limitations as regular variable names in PHP, ie they cannot start with a number". I guess this was a side effect of register_globals. Curiously, the docs no longer state this. Perhaps this limitation was removed when the register_globals option was removed in PHP 5.4.0

To elaborate on that a little bit the reason it didn't work with register_globals is because of how PHP treats super global variables such as $_SESSION. One of the things that makes a super global special is that it exists in all scopes without needing to use the 'global' keyword. The other thing is that it creates variables for all of the child elements automatically... again in all scopes. So if you have something like
$_SESSION['username'] = 'Levi';
That would create an additional variable $username which is equal to 'Levi'. So in the example above when you set a
$_SESSION[1] = 'Test';
PHP is going to try and set a variable $1 = 'Test'; Which is not possible