My file structure is as follows

xampp>httpdocs>reports>index.php, SalesByCustomer.php, SalesByCustomer.view.php, koolreport folder

When i am running - http://localhost/reports/index.php

This is the error coming - Fatal error: Class 'Sort' not found in C:\xampp\htdocs\reports\SalesByCustomer.php on line 29

Note - I am using xampp and my PHP Version is 5.5.30 Please guide.

Fatal error: Class 'Limit' not found in C:\xampp\htdocs\reports\SalesByCustomer.php on line 33

alright, 1st report is working now, i'll move next , my main requirement is to download pdf and excel files

Its seems for me that even the Koolreport class is also found "[Fri Jan 18 16:49:48.459827 2019] [:error] [pid 16902] [client 127.0.0.1:57168] PHP Fatal error: Class 'koolreport\koolReport' not found in /var/www/html/my_koolreport/SalesByCustomer.php on line 7, referer: http://localhost/". Just trying the first report example under Getting started page.

Its seems that this line is the issued: 7 class SalesByCustomer extends \koolreport\KoolReport

If you see from the code line, the case sensitive is correct. Same manner have from Cube class when trying this example: cube_customers_vs_categories

[19-Jan-2019 22:57:25 Europe/Berlin] PHP Fatal error:  Class 'koolreport\processes\Cube' not found in /Applications/MAMP/htdocs/my_koolreport/SalesCustomersProducts.php on line 34

Thanks a lot for your help. I fixed the case sensitive issue, but now I have another issue: here is my code (SalesByCustomer.php) as copied from example code:

<?php
        require_once "koolreport/autoload.php";
        use \koolreport\processes\Group;
        use \koolreport\processes\Sort;
        use \koolreport\processes\Limit;

        class SalesByCustomer extends \koolreport\KoolReport
        {
.........................

but still not found the class:

[Sun Jan 20 18:20:33.219734 2019] [:error] [pid 29101] [client 127.0.0.1:32926] PHP Fatal error:  Class 'koolreport\\KoolReport' not found in /var/www/html/my_koolreport/SalesByCustomer.php on line 7, referer: http://localhost/

for some reason a second backslash is added.

KoolReport class although existed in /var/www/html/my_koolreport/koolreport/src/KoolReport.php so maybe due to the second backslash, the code cannot find it.

Just found here: https://stackoverflow.com/questions/32083903/class-not-found-error-in-php-with-double-slashes that the double slashes output is just a way that php logging. So I cannot find any other reason that the code cannot find the class. As I just copied the code exactly from the example, the only thing that I can think is that maybe a config issue with PHP is took place here.

Finally I found a solution. Its seems that has to do with folder koolreport permissions and file owner. I changed the owner of all files to those that run the Apache (www-data) and change the permissions to 755. PHP Version 7.0.32-0ubuntu0.16.04.1

Yes, indeed. Thanks a lot for your help!!