htaccess - detect mod_php - .htaccess

Question

I'm trying to limit/eliminate duplication.
According to my (limited) understanding of some LAMP hosting providers (especially on shared servers) there are some PHP-ini directives that are ignored when set inside the PHP-script, but is accepted when set in the .htaccess; the process-flow should be quite simple:
detect any mod_php* -and set an environment variable if found
check this environment variable and set all php_value directives ONCE
redirect all requests to PHP for handling requests according to config
The objective is to withhold all content unless PHP is available to handle the request according to config -- per user/bot/api/etc. ..and by this obviously not serve any PHP-code as text O_o
I have no idea why this has to be any more complicated, but I refuse to accept that I have to duplicate a (long) list of php_value directives 4 times -- just because the Apache-conf is too (expletive deleted) to handle the simplest logical conditions .. (face-desk) .. or maybe i just don't know enough about Apache-conf, please help; the code below throws a 400 error, and I can't get it to work unless I duplicate each block for every php-version -and each hosting provider's own mod_php*suffix -for PHP-version-hot-switching.
Here's what [bl/thr]ows:
<IfModule mod_rewrite.c>
RewriteEngine On
RewriteBase /
<IfModule mod_php_null.c>
SetEnv MODPHP 1
</IfModule>
<IfModule mod_php5.c>
SetEnv MODPHP 1
</IfModule>
<IfModule mod_php7.c>
SetEnv MODPHP 1
</IfModule>
<If "%{ENV:MODPHP} =1">
php_value expose_php Off
php_value short_open_tag On
php_value display_errors On
php_value max_execution_time 60
php_value default_charset UTF-8
# list shortened for brevity
RewriteCond %{DOCUMENT_ROOT}/.auto.php -f
RewriteRule ^(.*)$ .auto.php [L]
</If>
</IfModule>

Answer 1

The code below works, however; note that:
<IfModule mod_authz_core.c> is used to verify Apache2.4 -for <If>
RewriteRule is used to define the variable
REDIRECT_ is (conditionally) prefixed to the variable name
RewriteCond %{ENV:MODPHP} ^1$ is used to test if the variable is 1.
<IfModule mod_rewrite.c>
<IfModule mod_authz_core.c>
RewriteEngine On
RewriteBase /
<IfModule mod_php_null.c>
RewriteRule .* - [E=MODPHP:1]
</IfModule>
<IfModule mod_php5.c>
RewriteRule .* - [E=MODPHP:1]
</IfModule>
<IfModule mod_php7.c>
RewriteRule .* - [E=MODPHP:1]
</IfModule>
<If "%{ENV:REDIRECT_MODPHP} =1">
php_value expose_php Off
php_value short_open_tag On
php_value display_errors On
php_value max_execution_time 60
php_value default_charset UTF-8
</If>
RewriteCond %{ENV:MODPHP} ^1$
RewriteCond %{DOCUMENT_ROOT}/.auto.php -f
RewriteRule ^(.*)$ .auto.php [L]
</IfModule>
</IfModule>