How to reference a file locally within my class

Question

I'm trying to use file_get_contents to reference a .json file in my module.

My directory structure is as follows

my custom field which is trying to reference the json file

/models/fields.stackexchangesites.php

my json file

/media/js/sites.json

If I use

    $json = 'modules/mod_kou_stack_exchange/media/js/sites.json';
    $json = file_get_contents($json);

PHP cannot find the file. I think perhaps because it is trying to reference it from the original file location. If I put the full location in the file it works, so long as I add an exception in Admin Tools. I don't want to hard code the URL as it might be used on other sites.

So then I have the option to use the URI function in Joomla.

https://docs.joomla.org/URLs_in_Joomla

However, if I try to use

use Joomla\CMS\Uri\Uri;
$uri = Uri::getInstance();
$url = $uri->toString();

within my code, it is then not accessible within the class that I am using

class JFormFieldStackexchangesites extends JFormFieldList

If I try to add use $uri and $url within the class that doesn't work either.

I'm sure this must be something to do with scope but having tried a few different ways I can't understand how to get it working.

Can anyone help me to understand how to get this working? And can anyone help me to understand why a relative path doesn't work?

Answer 1

Don't use JUri for fetching local files. It returns the web address of your site. Fetching files over HTTP is extremely slow compared to fetching files locally. Use one of JPATH constants to get a local filesystem path, e.g.:

$json = JPATH_BASE . '/modules/mod_kou_stack_exchange/media/js/sites.json';
$json = file_get_contents($json);

https://docs.joomla.org/Constants

Answer 2

Use the filepath:

JUri::base() . '/modules/mod_kou_stack_exchange/media/js/sites.json'

The filesystem equivalent of, eg. /public_html/yoursite/modules/... or /htdocs/yoursite/modules/... where Joomla is installed in yoursite directory.