Can't access session data session_write_close

Question

I was having issues with the session file being locked, so I added session_write_close() once I was done with the session. The script worked properly before that, however, once I leave the sign-in page now, the session is blank.

Session is started at the top of index.php which includes the sign in page:

$result = 'token_valid';
$_SESSION['user'] = $email;
print_r($_SESSION);
session_write_close();
print_r($_SESSION);

The session data is returned properly both times on the sign-in page.

Array ( [user] => abc@gmail.com ) Array ( [user] => abc@gmail.com )

A link returns to the home page, which calls a function to check if logged in...

function user_is_signed_in() {
    print_r($_SESSION);
    session_write_close();

    if($user == '') {
        return False;
    }
    else {
        return True;
    }

}

The session no longer has any data.

Full index.php

<?php 

session_start();

include_once('fnc/database.php');
include_once('fnc/user.php');

if(!user_is_signed_in()) {
  include('sign-in.php');
}
else {
  $url = parse_url($_SERVER['REQUEST_URI']);
  if(!$url['query'])
  {
    include('home.php');
  }
  else {
    if(isset($_GET['media']))
    {
      include($_GET['media'].'.php');
    }
    if(isset($_GET['user']))
    {
      include($_GET['user'].'.php');
    }

  }

}

.

.

Workaround (probably filthy)

Issue seems to be caused by the reading/writing of the actual session file. Used the session_id generated by PHP and just created a secondary session file. Do not save in same folder (or if you do, change the filename) - session_start seems to delete and regenerate the session file PHP manages and you'll lose any data written there.

session_start();
$sess = array();
$sess = $_SESSION;
$sess["id"] = session_id();
//print_r($sess);
session_write_close();

Create session_data in session folder

        $session_details = "user|".$email;

        $session_file = "/Programs/XAMPP/tmp/session_data/sess_".$sess["id"];
        //echo $session_details;

        $fh = fopen($session_file, 'w+');
        fwrite($fh, $session_details);
        fclose($fh);

Read session data from this file instead of the session

    $session_path = "/Programs/XAMPP/tmp/session_data/sess_".$sess["id"];
    $fh = fopen($session_path, 'r');
    $session_file = fread($fh, filesize($session_path));

    $exploded_session = explode("\n", $session_file);

    $session_data = array();

    foreach($exploded_session as $line)
    {
        $tmp = explode("|", $line);
        $session_data[$tmp[0]] = $tmp[1];
    }

    return $session_data["user"];

    fclose($fh);