Newsgroups: php.internals
Path: news.php.net
Xref: news.php.net php.internals:111181
MIME-Version: 1.0
Date: Fri, 24 Jul 2020 13:53:58 -0700
Message-ID: <CAB2bceYYB6GpuPU=zdMZi-Xo7=jO9DdhGFEBnWwyqsQ5wagwrQ@mail.gmail.com>
To: internals@lists.php.net
Content-Type: multipart/alternative; boundary="0000000000000969ee05ab362c54"
Subject: Proposal: php.ini environment variable fallback value
From: derek@derekbonner.com (Derek Bonner)

--0000000000000969ee05ab362c54
Content-Type: text/plain; charset="UTF-8"

Currently an environment variable can be specified in the php.ini file.
This is useful if you want tune one or two settings in your runtime
environment. Where this runs into issues is if you want to do something
similar to Juan Terminio[1][2].

I'm proposing a change the php.ini parser that would allow for an extended
syntax for environment variables in the php.ini. In this syntax when
checking for an environment variable if it is empty the fallback value
would be used instead. The original environment variable syntax would
remain valid as well.

Possible syntax options. I currently do not have a very deep understanding
of the current .ini parser so this may make invalid assumptions.

* memory_limit = ${PHP_MEMORY_LIMIT:-"default value"}
* memory_limit = ${PHP_MEMORY_LIMIT::"default value"}
* memory_limit = ${PHP_MEMORY_LIMIT:="default value"}
* memory_limit = ${PHP_MEMORY_LIMIT=="default value"}

* Potential issue: Adopting a bash-ism

This type of environment fallback is common in bash. If adopted it could
lead users to think other bash features are also available. To dissuade
this I would suggest that the fallback value syntax not appear in any of
the default php.ini files. Users must read the documentation and decide if
it works for them and add it in their php.ini file.

Changes needed in the code

Digging through the code I find that two sections would need to be changed,
both in Zend/zend_ini_parser.y. I hope to be able to write this code myself
but would gladly accept some guidance.

1. cfg_var_ref: Currently TC_DOLLAR_CURLY TC_VARNAME '} would need to be
changed to something like TC_DOLLAR_CURLY TC_VARNAME ':-' TC_FALLBACK '}'
2. zend_ini_get_var: I imagine this would require adding a third parameter
to the function signature that would be used in the event of a null value
when checking the environment.

[1]
https://jtreminio.com/blog/php-modules-toggled-via-environment-variables/
[2]
https://jtreminio.com/blog/docker-php/php-fpm-configuration-via-environment-variables/

I look forward to your feedback.

Derek

--0000000000000969ee05ab362c54--