Handle Joomla 404 errors gracefully in 5 lines of code: Fr: Redirection erreur 404 vers un article Joomla en 5 lignes de code / En: Redirect incoming 404 errors to custom Joomla article in 5 lines of code

error.php

<?php
/** Redirection vers article personnalisé */
if ($this->error->getCode() == 404) { 
  header(sprintf('Location: %s', \Joomla\CMS\Router\Route::_('index.php?option=com_content&view=article&id=64', false, \Joomla\CMS\Router\Route::TLS_FORCE, true)));
  exit(0);
}

En: Code snippet to put in error.php in your favourite template. Normally it should work. You can adapt the code as you wish to suit your needs but as-is it should work.

Fr: Bout de code à mettre dans le fichier error.php dans votre template préférée. Normalement ça devrait marcher. Vous pouvez adapter le code comme vous le souhaiter pour répondre à votre cas d'utilisation,mais, encore une fois, normalement ça devrait fonctionner.

this does not make a valid 404 page

Hi @brianteeman. Why is that? You just need to change the article id to match the article you want as 404 page. A joomler friend tried it and it works for him. Now having higher convertion rate even in case of the dreaded 404 page. Can you please tell me your use case. I'm curious to know why it didn't work for you.

To elaborate on the instructions to make this work:
1 - Create a Joomla article in your admin or frontend that will be used as custom 404 page.
2 - In the admin area make use you get the id of the article eg: 64
3 - Create hidden menu link using this single article and name it for example : What do you want to do?
4 - The alias of this article would be what-do-you-want-to-do
5 - If using Cassiopeia, for example. Create a child template named custom 404 (cassiopeia_custom_404)
6 - Create an override of the error.php by copying the error.php file from cassiopeia parent template in custom 404 child template.And copy the code snippet above without the opening php tag, below the use statements approximately line 17 in cassiopeia_custom_404 error.php you just copied from cassiopeia parent template.
7 - Save the error.php file
8 - Affect the menu link you created to this child template
9 - Type a non-existing url on your Joomla website.
10 - It should redirect you to the What do you want to do? custom 404 Joomla article page.

That's it. A more complete version of the 5-line php snippet.

This is not a 404 page. A 404 page has a status code of 404

This gist results ina statuse code of 302 (redirect) followed by a 200 (ok)

@brianteeman I understand your point and your concern. I should rename the title of this gist to be more precise and correct: How to handle 404 errors gracefully and redirect it to a custom Joomla article in 5 lines of code. The goal is to maximise the end-user of your site to see what you want them to see eg: special offer, a mailing list form, etc... Rather then a dull error that non tech-savvy people will understand. That is the use case that brought be to make this script. It was for a joomler friend that ask me how to do this as easy for him as possible. 5 lines is the best I could do for now.

The solution you offer here also used to be on the joomla docs site until it was pointed out that it is not a 404 page

https://docs.joomla.org/Archived:Creating_a_Custom_404_Error/en

Indeed. Blast from the past. Again @brianteeman I know you are absolutely right and this is not a 404 page. I rephrased it to be more clear. I changed the title. But that what my joomler friend's client wanted. Strictly speaking it is not a 404 page just as Joomla Web Services does not abide strictly to Roy Fielding's dissertation about REST. But as "real life, real world" examples and use cases occur we have to use what works for us. My friend's client is happy. So, to me, that's all that counts. One last thing. No-one is forced to use this script. If it does not fit someone's preferences they can freely ignore it. This is not a fight. I understand your point and I know you are right.