SHould also include a note about GPL 2-or-later for MediaWiki for compatibility

Update done in https://se.wikimedia.org/w/index.php?title=Developer_guidelines&type=revision&diff=87827&oldid=84094
@Sebastian_Berlin-WMSE @kalle @Alicia_Fagerving_WMSE Does this look ok and in line with what we discussed?

Perhaps being super clear with an example of PHP file comment rather than just a reference to the @license tag, so that people don't use class level comments (as I did).

* For php: Add the following to a comment in the top of each file. <code>@license <license></code>

vs

* For php: Add a file-level PHPDoc comment with license tag in the top of each file, above the use-statement and below any potential namespace-statement. <code>
<?php

namespace Foo

/** 
  * @file
  * @license <license>
 */

use \Bar;
</code>

Or something along that path.

How about the phrasing below?
* For php: Add a PHPDoc <code>@license <license></code> comment to the top of each file, above the use-statement and below any potential namespace-statement.<ref>See e.g. [https://gerrit.wikimedia.org/r/plugins/gitiles/mediawiki/extensions/Wikispeech/+/d9cf68ea3e5e02104ad0c70f4beec1578b67718b/includes/SpeechoidConnector.php|this example file].</ref>

Sure!

In T234596#6621317, @Lokal_Profil wrote:

Update done in https://se.wikimedia.org/w/index.php?title=Developer_guidelines&type=revision&diff=87827&oldid=84094
@Sebastian_Berlin-WMSE @kalle @Alicia_Fagerving_WMSE Does this look ok and in line with what we discussed?

Looks good to me.

In T234596#6621353, @Lokal_Profil wrote:

How about the phrasing below?
* For php: Add a PHPDoc <code>@license <license></code> comment to the top of each file, above the use-statement and below any potential namespace-statement.<ref>See e.g. [https://gerrit.wikimedia.org/r/plugins/gitiles/mediawiki/extensions/Wikispeech/+/d9cf68ea3e5e02104ad0c70f4beec1578b67718b/includes/SpeechoidConnector.php|this example file].</ref>

added