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$PCNAME = strtoupper(getenv("COMPUTERNAME"));

getenv returns no result or returns a empty string

expected: the name of Windows PC (COMPUTERNAME) 

the same line in php 7 works as expected

Hmm, works for me with the CLI Sapi.  Which SAPI/Webserver do you
use?  Also make sure to check the output of

    var_dump(getenv("COMPUTERNAME"))

Does you COMPUTERNAME contain non-ASCII characters?

in phpinfo(); is no entry 'COMPUTERNAME' under Environment

var_dump(getenv("COMPUTERNAME")) => bool(false)

apache 2.4 php8 32 bit
ScriptAlias /php8 "C:/web/php8_32bit"
<Directory "C:/web/php8_32bit">
    AllowOverride None
    Options None
    Require all denied
    <Files "php-cgi.exe">
        Require all granted
    </Files>
</Directory>

<Directory "C:\web\Apache24\htdocs\burz_auftraege">
    UnsetEnv PHPRC
    <FilesMatch "\.php$">
        SetHandler application/x-httpd-php8
        Action application/x-httpd-php8 "/php8/php-cgi.exe"
    </FilesMatch>
</Directory>

my PCNMAE is 'SPERLINGPROG'
__________________________________________________
with php7 ( same apache ) it works but over:
LoadModule php7_module "C:\web\php7_32bit\php7apache2_4.dll"

Thanks for the swift reply!

> with php7 ( same apache ) it works but over:
> LoadModule php7_module "C:\web\php7_32bit\php7apache2_4.dll"

Ah, so this is not a behavioral change in PHP 8, but rather a
behavioral difference between running PHP with Apache as module
and as (F)CGI, respectively.  It is actually not even a bug
regarding PHP, but rather a configuration issue of Apache.  Please
consult the respective Apache documentation and/or support
channels.

By the way, did you deliberately switch to (F)CGI?

... By the way, did you deliberately switch to (F)CGI? ...

I needed different versions of php for different directorys. AND I found this way to solve.

Is there a better way? Or why du U ask?

> I needed different versions of php for different directorys.

Ah, okay, makes sense.  I wondered whether you had issues setting
up PHP 8.0 as Apache module.