I am trying to use Xdebug for magento 1. However, Xdebug no longer supports PHP under 7.0. Magento 1 on the other hand only works for php 5.
You can download older versions of xdebug which are compatible with php 5.
You can see and download all the versions released till now here - https://xdebug.org/download.php
Just scroll down and look for a compatible version to your corresponding php.