PHP has been around for a while and therefore you will find a lot off sites that use it and people who are familiar with it. Most people do not like to change so most of those people will recommend PHP.
Python is a scripting language and Django uses it to get its job done. Django is newer and you will have a harder time finding people who know it and sites that use it. Craigslist.org is probably the most well known site that uses django.
HTML was great when it came out, but has its limitations. You are basically stuck with using static web pages that need a lot of administrative work to update and maintain.
PHP was an innovation that reduced this administrative work, but you have to build a lot of boiler plate. With PHP (and its brother APS.net) you will spend a lot of time creating and maintaining things that will never be seen directly on your website.
Django (and drupal) are the next generation for web development. It reduces a lot of the boilerplate work so you spend more time on the visible aspects of your website. I personally do not care for drupal because it does too much behind the scenes for me and I like a little more control.
If you are learning something to make a new website and do not want to learn both, my vote is that you learn python/django. PHP is a dead end and destine to go the way of fortran and cobol.
First learn HTML and CSS. You will not get anywhere without that. I recommend Build Your Own Web Site The Right Way Using HTML & CSS by Ian LLoyd.
I then recommend The Definitive Guide to django Web Development Done Right by Adrian Holovaty and Jacob Kaplan-Moss or the free online version: http://djangobook.com/.