Description:
------------
My apologies if this is a dup, I've searched and searched and found nothing.

php.ini [relevant]:
session.save_handler = files
session.save_path = /tmp
session.use_cookies = 1
session.use_only_cookies = 1
session.name = PHPSESSID
session.auto_start = 0
session.cookie_lifetime = 0
session.cookie_path = /
session.cookie_domain =                                                                                                    
session.serialize_handler = php

As commented in the code, the $_SESSION variable is not correctly set when both $array[1] and $array['string'] are set. 

Reproduce code:
---------------
<?php
                                                                                                    
session_start();
                                                                                                    
//this is our goal, to get here.
if(isset($_SESSION['allSet'])){
  print_r($_SESSION);
  session_destroy();
}
//start the test.
else{
  /* this numeric key creates the problem.
   commented out "$basic_array[0] = 4;" and this code will work fine,
   otherwise we have an infinite redirect. */
  $basic_array[1] = 4;
                                                                                                    
  $basic_array['user_id'] = 4;
  $basic_array['email'] = "rob@rob.com";
                                                                                                    
  foreach(array_keys($basic_array) AS $key){
    $_SESSION[$key] = $basic_array[$key];
  }
                                                                                                    
  $_SESSION['allSet'] = 1;
  header("Location: http://FULLPATHTOSERVER/LOGINTEST.php");
}


Expected result:
----------------
The $_SESSION variable should contain all the relevant data.

Actual result:
--------------
$_SESSION contains no data, despite being set.