[stable19] Add php docs build script

[juliusknorr]

backport of #22432 and #22447

[faily-bot]

🤖 beep boop beep 🤖

Here are the logs for the failed build:

Status of 32377: failure

mysql5.6-php7.2

Show full log

There were 2 warnings:
1) Test\Files\ViewTest::testRenameFailDeleteTargetKeepSource
Trying to configure method "writeStream" which cannot be configured because it does not exist, has not been specified, is final, or is static
2) Test\Files\ViewTest::testCopyFailDeleteTargetKeepSource
Trying to configure method "writeStream" which cannot be configured because it does not exist, has not been specified, is final, or is static
--
There was 1 failure:
1) OCA\Files_Versions\Tests\VersioningTest::testRestoreMovedShare
File content has not changed
Failed asserting that two strings are equal.
--- Expected
+++ Actual
@@ @@
-'version 2'
+'version 1'
/drone/src/apps/files_versions/tests/VersioningTest.php:730