Inconsistent passage of session variable between pages - php

Question

I'm having a problem passing a session variable from one page to another- in only ONE situation.
The problem is that sometimes the variable passes, sometimes, not.
About 50% of the time I need to refresh the second page (multiple times) to read the variable correctly.
When it doesn't read the "new" variable, the "old" session variable is used and brings up a different person.
I'm not "losing" the variable, it's just that the "new" variable isn't being read by the page.
Here's the layout:
.............................Page A
...............................|
...............................|
.............................Page B
...............................|
.............__________________|___________________
.............|.................|..................|
___________Page C...........Page D..............Page E
Page A is a list of people in rows taken from a db.
When you click on a row it "selects" the person with this code:
$("#patienttable tr").click(function() {
var passthis = $(this).find("#localid").html();
$.post("php/setsessionvariable.php",
{sessionval: passthis} );
window.location.href = 'http://www.xxxxxxxx.xxx/xxxxxx/xx/xxxx.php';
});
"patienttable" is the list of people.
"passthis" is the person identifier (from "localid").
"setsessionvariable.php" is the server side php file that sets the variable.
Here is the php file that sets the session variable (pretty boring, huh?)
<?php
session_start();
$_SESSION['patientidentifier'] = $_POST['sessionval'];
?>
In pages B, C, D, and E, the session variable is read by php code on the same page as the HTML, like this;
These are the first lines at the top of the file.
<?php
session_start();
$ptidentifier = $_SESSION['patientidentifier'];
...rest of php code to pull data from the db and post it on the page...
...html code...
...javascript code...
...end of page...
I have NEVER had a problem with moving from Page B to C, Page B to D, Page B to E, and back and forth...NEVER.
The problem is always from Page A to B.
Questions:
Can someone point me in the right direction to fix this?
Would you set a session variable like this? or a better way?
I thank you in advance.

Answer 1

your not finishing the post before redirecting to the next page. change your code as follows. it will then allow your post to finish before redirecting to the next page.
$("#patienttable tr").click(function() {
var passthis = $(this).find("#localid").html();
$.post("php/setsessionvariable.php",
{sessionval: passthis} , function (e) {
window.location.href = 'http://www.thedentons.us/easyehr/v2/root.php'
} );
;
});