Ajax call returns 0 when add_action is inside a class in functions.php

Question

Ajax call returns 0 as output. I am sure that hook is not working and it's not calling the test2 method. Why is add_action(... not working inside class in functions.php?

--------Wrap inside functions.php Starts-------

class test{
    public function __construct() {
        add_action( 'wp_ajax_test2', array( $this, 'test2' ) );
    }                       
    public function test1() { ?>
        <script>
            jQuery(document).ready(function($){
                var ajaxurl = "<?php echo get_site_url();?>/wp-admin/admin-ajax.php";
                var data = {'action':'test2'};
                 $.ajax({   
                    url: ajaxurl,
                    type: "POST",
                    data: data,
                    success: function(val) {
                        alert(val);
                    },
                }); 
            });             
        </script><?php 
    }               
    public function test2(){
        echo "success";
        exit;
    }       
}

--------Wrap inside functions.php Ends-------

Created an object in a template page and call to test1 method:

$ob_call = new test;
$ob_call->test1();

Answer 1

While I am not sure why you want to do it like this, please find below the working code. Please note the comments in line. I hope this helps.

class test{
    public function __construct() {
        add_action( 'wp_ajax_test2', array( $this, 'test2' ) );
        /* Front end ajax needs this. */
        add_action( 'wp_ajax_nopriv_test2', array( $this, 'test2' ) );
        add_action( 'wp_enqueue_scripts', array( $this, 'test1' ) );
    }

    public function test1() {
      /* in JavaScript, object properties are accessed as ajax_object.ajax_url, ajax_object.we_value */
      wp_localize_script('test-script-ajax', 'ajaxobj', array('ajaxurl' => admin_url('admin-ajax.php')));
      /* Moved your js to a separate js file and enquing it the WordPress way */ 
      wp_enqueue_script( 'test-script-ajax', get_stylesheet_directory_uri() . '/js/test-ajax.js', array( 'jquery' ));
    }

    public function test2(){
        echo "success";
        exit;
    }
}

$ob_call = new test;
$ob_call->test1();

Here is the code in test-ajax.js file

jQuery(document).ready(function($){
  var data = { 'action':'test2' };
  jQuery.post( ajaxobj.ajaxurl, data, function( response ) {
            alert(response);
    });
});

Answer 2

Add wp_die(); at the end the your function.

Answer 3

It works now

----------Function.php---------------

add_action( 'wp_ajax_test2', array( 'test', 'test2' ) );

class test{

    public function __construct() {
        
    }                       
    public function test1() { ?>
        <script>
            jQuery(document).ready(function($){
                var ajaxurl = "<?php echo get_site_url();?>/wp-admin/admin-ajax.php";
                var data = {'action':'test2'};
                 $.ajax({ 
                    url: ajaxurl,
                    type: "POST",
                    data: data,
                    success: function(val) {
                        alert(val);
                    },
                }); 
            });             
        </script><?php 
    }               
    public function test2(){
        echo "success";
        exit;
    } 
          
}

---

------------------page (Template)-------------

$ob_call = new test;

$ob_call->test1();

Have a look to https://wordpress.stackexchange.com/questions/203383/why-hooking-differs-in-plugin-and-function-php-wordpress