In my case, I did remove all log file in var (or you can backup it) then re-run export function. After that go to var/log and found an exception.
Open log and see that function
I go to php.ini and found that the function in list disable function config. I remove it from list then it works.
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Magento does not save Product data in a single table. It is using an Eav Structure for saving Product attribute data.So first you have to understand this Eav structure then you able to get your required data.
you can use the code below to add the category names in separate columns in csv file, just modified your code a bit.
$products = Mage::getModel('catalog/product')->getCollection();
Better we can use below code to get required attributes from collection instead of '*'
require __DIR__ . '/app/bootstrap.php';
$bootstrap = Bootstrap::create(BP, $_SERVER);
$objectManager = $bootstrap->getObjectManager();
$state = $objectManager->get('Magento\Framework\App\State');
If you are using a CDN, for example CloudFlare CDN, it is advised not to use this on the admin as it will cause problems such as this issue as well as cross-origin problems with editing CMS pages as another example. This issue CloudFlare says is due to a mismatching in header buffer sizes.
Please use CDN only in website scope, not in the global scope.