$.ajax asynchronous request failing?

Question

PHP

An asynchronous request does not work, I have been suffering for 8 hours already, I watched a ton of video tutorials, I seem to be doing everything right.
There is an assumption that the url is not correctly specified, but I tried it this way and that :(
Here is the javascript itself, its location can be seen on the left (I highlighted it)


And here is php itself, where, in theory, I send the request

Answer 1

That's it, I figured it out, thanks to everyone, the error was that I connected to the class that connects to the main page, respectively, knocked out errors, there is no connection type to the database, etc., redirected to the main page where this class is connected and everything worked great :)

Answer 2

and if you add dataType when calling ajax?

Answer 3

Use the browser console - this is perhaps one of the best friends of a WEB developer, it simplifies life at times))
firebug for example or built-in.

Answer 4

How do you determine what doesn't work? Open the development tools, take a look at the network, and see what goes where.

Answer 5

Try prefixing engine/classes... with a slash /engine/classes...

Answer 6

What if we add return false to the end of the button click handler?

Answer 7

debug
in the browser console, see where the request goes, set a
breakpoint in index.php and see where the route goes