PHP is as general-purpose scripting language geared towards web development and often used in those contexts. Nevertheless it is not common known that the licensing behind the software is more out of a problem and making it more than only a lightweight issue packaging this for a free and libre operating-system. To be clear: It is not possible to package PHP for a free and libre system without getting into trademark-issues when modifying without “explicit” permission.

Starting in the year 2000, the PHP authors have decided to remove the option to use PHP under the General Public License, so with beginning from PHP version 4. This left users with only the PHP License as an option, which is non-copyleft, but includes extra restrictions beyond most licenses.

 [...]

  3. The name "PHP" must not be used to endorse or promote products
     derived from this software without prior written permission. For
     written permission, please contact group@php.net.
     
  4. Products derived from this software may not be called "PHP", nor
     may "PHP" appear in their name, without prior written permission
     from group@php.net.  You may indicate that your software works in
     conjunction with PHP by saying "Foo for PHP" instead of calling
     it "PHP Foo" or "phpfoo"
     
   5. The PHP Group may publish revised and/or new versions of the
     license from time to time. Each version will be given a
     distinguishing version number.
     Once covered code has been published under a particular version
     of the license, you may always continue to use it under the terms
     of that version. You may also choose to use such covered code
     under the terms of any subsequent version of the license
     published by the PHP Group. No one other than the PHP Group has
     the right to modify the terms applicable to covered code created
     under this License.

 [...]
 

(Source: PHP 3.01 License)

Those restrictions specifically related to use of the PHP name. Ultimately, such licensing makes extra work for system-distributions and operating-systems and creates uncertainty for people wishing to modify PHP - as they navigate a license that awkwardly pulls in a trademark policy as part of it.

In the whole outcome and as result PHP violates the freedom to redistribute without “explicit” approval. Especially to underline the concrete term again, which violates the freedom of redistribution directly:

Once covered code has been published under a particular version of the license, you may always continue to use it under the terms of that version.

So if we would do individual modifications corresponding our mission-statement, we would always have to ask and have nevertheless a legal issue opened.

The Hyperbola-project decided to completely remove PHP from its packages since the release of version 0.4.3 for Hyperbola GNU/Linux-libre and also for the future with HyperbolaBSD as complete operating-system. We don't provide problematic packages and software not respecting the freedom of the users to modify their systems and sources as they want. A trademark-policy can lead to a complete false balance when organizations and people behind decide to withdraw rights at once as it is always part of that trademark. And this withdrawal would immediate lead to further legal issues for projects and systems including those names and software!