Background: I was trying to install DokuWiki in my chrooted OpenBSD webserver. The install seemed funky (generated config but not ACLs), and the installer page, instead of even showing any errors, was just blank after submitting initial parameters. Long story short, I edited install.php to approximately this effect, and finally got a visible error, which let me find out that I needed to create $CHROOT/dev/{a,u,s,}random. I would have found that out a lot sooner and torn out a lot less of my beautiful hair if something like this were already in place. After all, the installation phase is where one expects many edge cases and whatnot. Would help newcomers with strange environments to make more actionable forum posts crying for help. Please consider.

This check was useful in ages past, when there was no conf/local.php

However, nowadays it causes the installer to fail with the snapshot
version of DokuWiki and since we now have a dedicated local.php, it has
become obsolete.

When a server has no PHP support enabled, it will either prompt to
download a PHP file or may display it as HTML instead. When a user tries
to run install.php with a server that does the latter, they will see
some weird garbage with the browser trying to interpret raw PHP as HTML.
This pathc adds a warning at the top, telling the user what is going on.

Access attempts to security.png are normally denied, so the name of the file will be more self-descriptive

Otherwise the it will fail with the following error:

	2017/02/20 14:34:57 [error] 16242#0: *59 FastCGI sent in stderr: "PHP message: PHP Fatal error:  Call to undefined function random_int() in /var/www/dokuwiki/inc/PassHash.class.php on line 630" while reading response header from upstream, client: 172.18.35.245, server: _, request: "POST /dokuwiki/install.php HTTP/1.1", upstream: "fastcgi://unix:/var/run/php-fpm/php-fpm.sock:", host: "10.5.234.170", referrer: "http://10.5.234.170/dokuwiki/install.php"

Fixes #1852

In an older version of PHP a file_exists() call would issue a warning
when the file did not exist. This was fixed in later PHP releases. Since
we require PHP 5.3 now, there's no need to supress any error here
anymore. This might even give a minor performance boost.

that's the version in Debian old stable

this adds the ability to place a install.conf file next to the
install.php which contains additional config options to be written to
conf/local.php on completion of the installer. The install.conf is
automatically deleted then.

This is useful for automated DokuWiki installers or downloaders that
take care of downloading DokuWiki and then drop the user in the default
install dialog for initial setup. These tools may set up host specific
things options like rewrites, image magic path or file permission
settings in this preset.

server side resizing now needs a security hash which we can' provide in
the installer, yet.

According to the documentation the function was removed in PHP 5.4.0
though it still seems to exist in my PHP 5.4.6 installation.