Get Decode Session Variables From PHPSESSID

session_decode.php

<?php

# .env file variables
# OLD_SESSION_PATH=/var/tmp/
# OLD_SESSION_PRF=sess_

function getUserIdFromOldSession()
{
    if( ! isset($_COOKIE['PHPSESSID']) ){
        return false;
    }

    $phpsessid = $_COOKIE['PHPSESSID'];
    $sessionFile = env('OLD_SESSION_PATH').env('OLD_SESSION_PRF').$phpsessid;

    if( ! is_file($sessionFile) ){
        return false;
    }

    $data = file_get_contents($sessionFile);

    $session_decode = function ($serialized_string)
    {
        $variables = array();
        $a = preg_split( "/(\w+)\|/", $serialized_string, -1, PREG_SPLIT_NO_EMPTY | PREG_SPLIT_DELIM_CAPTURE );

        for( $i = 0; $i<count($a); $i = $i+2 )
        {
            if(isset($a[$i+1]))
            {
                $variables[$a[$i]] = unserialize( $a[$i+1] );
            }
        }
        return( $variables );
    };


    $session = $session_decode($data);

    if( isset($session['UserID']) && $session['UserID'] > 0 ){
        return $session['UserID'];
    }

    return false;
}