Ajax and PHP - why does the whole page load instead of a specific block?

Question

JavaScript

I'm building a website right now and I'm having a problem.
Using Ajax, you need to pull one of the blocks with a unique id on the page from a specific (static) php page.

$('.link_to_main').click(function() { 
  $('#page_content').load("my_file.php #my_container");
});

As a result of executing the code in '#page_content, the entire my_file.php is loaded.
There is a similar code, but the file my_file.HTML and everything works fine.
Tell me how you can deal with this, or at least in which direction to dig?

Answer 1

I usually do something like this.

$.ajax({
  url: "my_file.php",
  success: function (response) {
    $('#page_content').html( $(response).filter('#my_container').html() );
  }
});