Magento2

the easy way is to go to this file 

\vendor\magento\framework\Event\Manager.php

then go to this function dispatch

you can now user this 

foreach ($this->_eventConfig->getObservers($eventName) as $observerConfig) {
    if ($eventName == "catalog_product_save_after") {
         $all_observers = print_r($observerConfig, true);
    }
}

The most frequent question, asked by Magento users, is correct permissions. They can differ, whether you run your store in one-user mode, or many-user, and also can be different for different modes.

Single user mode

One-user mode is the simplest case. In this case user shall belong to group, which own Magento system and also runs web-server. For them the following rules apply:

The best easy way is to simulate the directory path, so lets assume you will need to fix the comparison page after you upgrade to Magento 2.3.5-p2

Filename: vendor/magento/module-catalog/Helper/Output.php

we need to replace this line 

- if (preg_match($pattern, $attributeHtml)) {

with this line 

+ if (preg_match($pattern, (string) $attributeHtml)) {

Now create those directories vendor/magento/module-catalog/Helper

To change the HasSpecialPrice value you need to create a new module then after that you can add this code to the etc/di.xml 

The best approche is to add these files  "checkout_cart_index.xml" and "checkout_index_index.xml" in this directory 

app/design/frontend/{Vendor}/{theme}/Magento_Checkout/layout/

with this content 

checkout_cart_index.xml

- https://www.magezon.com/magezon-page-builder-for-magento-2.html : Build CMS Page, CMS Block, Product Description and Category Description

- https://www.magezon.com/magento-2-blog-extension.html : Empower Your Magento Blog and Grab More Audiences

How many times you tried to install Magento 2 and later you could not see the website working !!, How many times you tried to search for these sentences 

"Magento 2 css not working"

"Magento 2 js not working"

"Magento 2 404 page not found" because of the static files?

Now here is the solution, and easily it is the missed .htaccess (for apache)

by quick look at this path "{magento root}/pub/static", you will see that you missed the .htaccess file

Go to the Nginx  configuration then you need to edit the line similar to this line 

location ~ (index|get|static|report|404|503)\.php$ {

to be like this 

location ~ (index|get|static|report|404|503|phpinfo)\.php$ {

then restart Nginx 

do you have this error always after each upgrade and you are not able to figure out which value cause this issue?

the best way is to debug the issue and find which one by going to this file 

\vendor\magento\framework\Serialize\Serializer\Json.php

go to this function 

You can use the Magento 2 CLI to do it, you can check your current search engine using:

php -f bin/magento config:show catalog/search/engine

if you want to change the engine to Elasticseach version 6 then use this command 

php -f bin/magento config:set catalog/search/engine 'elasticsearch6'