Error function main() is a non-object to construct my Ajax.php

Question

Try to use a "rapid" ajax, I've the follow code in my my-ajax.php file

define('SHORTINIT',true);
require_once ('../../../../wp-load.php');
require_once ('../../../../wp-config.php');
require_once ('../../../../wp-blog-header.php');
if ((!isset($_POST["action"])) || ($_POST["action"]!=="") || (!is_numeric($_POST["action"]))) {
    switch($_POST["action"]){
        case 'buscaPost':
            if ((isset($_POST["miPost"])) || (isset($_POST["slug"]))){
                echo "my actions";
                die();
            }else{
                echo "Fail!";
            }
            break;
    }   
}

I try to change the values of wp-load.php path but this is the correct path.

My file my-ajax.php is in

/www/wp-conent/themes/myTheme/folderTheme/myAjax/my-ajax.php

Edit:

I'm not sure if this is the correct way but I need WP_Query to use this in my ajax and now I include the follow requires:

require_once ('../../../../wp-load.php');
require_once ('../../../../wp-includes/taxonomy.php');
require_once ('../../../../wp-includes/meta.php');
require_once ('../../../../wp-includes/pluggable.php');
require_once ('../../../../wp-includes/post.php');
require_once ('../../../../wp-includes/query.php');

But I've the error

get_current_user_id() is not defined

This is include in the wp-includes/pluggable.php. Maybe exists other way to add this wordpress object (WP_Query)??

Now I've other problems with AUTH_COOKIE, LOGGED_IN_COOKIE (this constants are not defined) and call_user_func_array (this said: expect parameter 1 to be a valid callback).

My code actually is:

define('SHORTINIT',true);
define('AUTH_COOKIE',true);
define('LOGGED_IN_COOKIE',true);
// I add this define to correct the error who send me Wordpress, he said this constants are not defined
require_once ('../../../../wp-load.php');
require_once ('../../../../wp-includes/taxonomy.php');
require_once ('../../../../wp-includes/meta.php');
require_once ('../../../../wp-includes/post.php');
require_once ('../../../../wp-includes/user.php');
require_once ('../../../../wp-includes/pluggable.php');
require_once ('../../../../wp-includes/capabilities.php');
require_once ('../../../../wp-includes/query.php');
require_once ('ajax-funciones.php'); //some functions to returns values, actually only return "hi everybody".
if ((!isset($_POST["action"])) || ($_POST["action"]!=="") || (!is_numeric($_POST["action"]))) {
    switch($_POST["action"]){
        case 'buscaPost':
            if ((isset($_POST["miPost"])) || (isset($_POST["slug"]))){
                sacaPost($_POST["miPost"],$_POST["slug"]);
                die();
            }else{
                echo "No hay variables";
            }
            break;
    }
}

What can be the mistake?

Other problem is: I've been put a function in my ajax-funciones.php like this:

function sacaPost($idPost,$slugPost){   
    // Buscamos el contenido del post
    $query = array("cat"=>$_POST["miPost"]);    
    $objetoDatos = new WP_Query($query);    
    if ($objetoDatos->have_posts()){
        while($objetoDatos->have_posts()){
            $objetoDatos->the_post();
            the_content();              
        }
        wp_reset_postdata();
    }else{
        echo "any";
    }   
}

And called this in my-ajax.php but always return "any" and I don't know the reason. It's necesary other way to rescue the values?