com_ajax call is hitting function but not returning result from other function call

Question

I'm using an ajax call that hits the immediate function fine, and then returns a dummy value via dump(). However, when I change it to call another function and get my data rather than using the dummy value, I'm getting a 500 error.

In Helper.php, This returns the value with a code 200:

public static function getStoresByZipAjax(){

    $input = JFactory::getApplication()->input;
    $zip  = $input->get("zip");

    dump($zip);

    //return $this->getStores($zip);
}

However, when I comment out the dump and reinstate the function call, it fails with a 500:

public static function getStoresByZipAjax(){

    $input = JFactory::getApplication()->input;
    $zip  = $input->get("zip");

    //dump($zip);

     return $this->getStores($zip);
}

public static function getStores($zip){
    $test = $zip;

    dump($test);
}

Here is my mod_hunter_maps_dev.php file:

<?php 
 //check joomla calling
defined('_JEXEC') or die;
require_once dirname(__FILE__) . '/helper.php';

$test = modHunterMapsDevHelper::getStores();


require JModuleHelper::getLayoutPath('mod_hunter_maps_dev', $params->get('layout', 'default'));
?>

What am I doing wrong here?

AJAX call for reference:

jQuery.ajax({
   type: 'GET',
   url: "<?php echo JURI::base() . "index.php?option=com_ajax&module=hunter_maps_dev&method=getStoresByZip&zip="?>"  +zip+ "&format=json",
   success:function(data){
       console.log('success');
   },
   error: function(xhr, status, error) {
       alert(xhr.responseText);
   }
 });

Answer 1

The fatal error will be: "PHP Fatal error: Using $this when not in object context"

You need to change

return $this->getStores($zip);

to

return self::getStores($zip);