Fonction getenv() VS la variable $_ENV

ini_get('variables_order')             === GPCS 
Fonction getenv('REQUEST_URI');        === /php/getenv.php 
Variable $HTTP_ENV_VARS['REQUEST_URI'] ===  
// only if E is in variables_order in .ini
// or overwrite with: php --define variables_order=GPCSE getenv.php
Variable $_ENV['REQUEST_URI']          ===  
Variable $_SERVER['REQUEST_URI']       === /php/getenv.php 
PHP_VERSION: 7.4.33