PHP：getenv（）无法读取的环境变量

I am using .htaccess file for setting an environment variable

SetEnv ENV "development"

It can be read by $_SERVER['ENV'] but not by getenv('ENV'); For getenv() I have to use

putenv('ENV=development');

Don't know why variable which is set in .htaccess is not readable by getenv().

Edit: Because I am using a foreign script where "ENV" is asked I did not realise that just the name "ENV" is causing trouble (reserved?). A test with just another environment variable name works as expected

SetEnv REDIRECT_ENV "development"

Edit 2: Environment is Apache 2.2, fastcgi, debian wheezy, php5.4.4 I noticed this behaviour on VirtualBox VM and on rooted server online with same components

You can do with mod_rewrite to detect env:

RewriteEngine on

RewriteCond %{HTTP_HOST} ^stage\.domain\.com$
RewriteRule (.*) $1 [E=PYRO_ENV:stage]

RewriteCond %{HTTP_HOST} ^www\.domain\.com$
RewriteRule (.*) $1 [E=PYRO_ENV:production]

and

SetEnvIf Host ^stage\.example\.com$ PYRO_ENV=stage
SetEnvIf Host ^(www\.)?example\.com$ PYRO_ENV=production