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[2007-09-27 04:10 UTC] johns582 at mail dot msu dot edu
Description:
------------
We use a function (see below) to populate variables based on whether there is a key present in the $_GET, $_POST, or $_SESSION arrays. After this function is called and the result assigned to a variable, we save the variable in a session with:
$_SESSION['var'] = $var;
The result of this statement is that the variable $var is successful stored in $_SESSION but is not saved to the session file, which is what we expect. We can correct the problem by taking the logic in the function below out of the function and placing it into the body of the main script. We've also noticed that even when the function is called by the main script, but not used to assign a value to a variable we intend to store in a session, this is enough to "break" the session in the manner described above (e.g.,
//DOESN'T WORK TO MAKE $f_name and $l_name appear in the session file
//even though we aren't actually storing the value of $f_name_p or //$l_name_p in the session. But works if lines 3 and 4 are removed.
$f_name = $_POST['f_name'];
$l_name = $_POST['l_name'];
$f_name_p = populate_rev ("f_name", $_GET, $_POST, $_SESSION);
$l_name_p = populate_rev ("l_name", $_GET, $_POST, $_SESSION);
$_SESSION['f_name'] = $f_name;
$_SESSION['l_name'] = $l_name;
One last point: This problem occurs with both the default "files" session handler and a custom db-backed handler. Using the db-backed handler, we can confirm that the overloaded "write" function received a session key, but no data.
Reproduce code:
---------------
function populate_rev ($array_index, $_GET, $_POST, $_SESSION) {
if (isset($_GET["$array_index"])) {
$var = $_GET["$array_index"];
}
elseif (isset($_POST["$array_index"])) {
$var = $_POST["$array_index"];
}
elseif (isset($_SESSION["$array_index"])) {
$var = $_SESSION["$array_index"];
}
else {
$var = '';
}
return $var;
}
Expected result:
----------------
Expected to see the string f_name|s:7:"Heather";l_name|s:7:"Johnson"; present in the session file or in the database (depending on which handler was currently being used), for example, following assignment of $f_name and $l_name to the corresponding key in $_SESSION and termination of the script.
Actual result:
--------------
Even though the $_SESSION array contains the expected key/value pairs, the session file or database row (in the case of our custom handler) doesn't contain them. No data is passed to the session write function in the case of the custom handler. Moving the function's logic into the main body of the script, or abandoning the function in favor of straight assignment from the $_POST vars array is the only way to produce the expected result. (e.g.,
$f_name = $_POST['f_name'];
$l_name = $_POST['l_name'];
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Last updated: Fri Jul 04 14:01:35 2025 UTC |
Sure - Here is the form from which the script can be invoked: <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"> <html> <head> <title>Test Sessions</title> </head> <body> <form action="/php/test_session.php" method="post"> <input type="text" value="" name="f_name"><br> <input type="text" value="" name="l_name"> <input type="submit" value="test session"> </form> </body> </html> And here is the script itself (it is currently set up to use a file-based session handler). There is some commented-out code in here that should make it easy to see how seemingly irrelevant adjustments to how the var is initially set will influence whether it gets set in the session file (or db row): <?php //include functions library include_once("php/libraries/general_functions_new.php"); session_start(); //if the var assignments are made directly from the _POST array, //then the session vars are successfully set //$f_name = $_POST['f_name']; //$l_name = $_POST['l_name']; //but setting the vars with a call to populate_rev, the subsequently //assigning them to $_SESSION results in a successful assignment to //$_SESSION, but no storage in the session file or db. $f_name = populate_rev ("f_name", $_GET, $_POST, $_SESSION); $l_name = populate_rev ("l_name", $_GET, $_POST, $_SESSION); //If code contained in populate_rev is brought into the main //body of this script, then the session vars are successfully set /* if (isset($_GET["f_name"])) { $f_name = $_GET["f_name"]; } elseif (isset($_POST["f_name"])) { $f_name = $_POST["f_name"]; } else { if (isset($_SESSION["f_name"])) { $f_name = $_SESSION["f_name"]; } else { $f_name = ''; } } if (isset($_GET["l_name"])) { $l_name = $_GET["l_name"]; } elseif (isset($_POST["l_name"])) { $l_name = $_POST["l_name"]; } else { if (isset($_SESSION["l_name"])) { $l_name = $_SESSION["l_name"]; } else { $l_name = ''; } } */ //register vars in the session $_SESSION['f_name'] = $f_name; $_SESSION['l_name'] = $l_name; echo "<br>Contents of global _SESSION array: "; var_export($_SESSION); echo "<br>Done writing session vars. Check session file or db to confirm."; ?> And here is the function library, general_functions_new.php: <?php function populate_rev ($array_index, $_GET, $_POST, $_SESSION) { if (isset($_GET["$array_index"])) { $var = $_GET["$array_index"]; } elseif (isset($_POST["$array_index"])) { $var = $_POST["$array_index"]; } elseif (isset($_SESSION["$array_index"])) { $var = $_SESSION["$array_index"]; } else { $var = ''; } return $var; } ?>Here is a version (12 lines) that doesn't have any of the commented out code. But I'd still recommend looking at the original, as the commented code was intended to save you time in reproducing some of the weirder behavior I described above. <?php include_once("php/libraries/general_functions_new.php"); session_start(); $f_name = populate_rev ("f_name", $_GET, $_POST, $_SESSION); $l_name = populate_rev ("l_name", $_GET, $_POST, $_SESSION); $_SESSION['f_name'] = $f_name; $_SESSION['l_name'] = $l_name; echo "<br>Contents of global _SESSION array: "; var_export($_SESSION); echo "<br>Done writing session vars. Check session file or db to confirm."; ?>