$_ENVを有効にする

PHPのデフォルトの設定では，スーパーグローバル変数 $_ENVが使用できない．使いたい場合には，php.ini の variable_orders を "EGPCS" に変更する．

; This directive determines which super global arrays are registered when PHP
; starts up. G,P,C,E & S are abbreviations for the following respective super
; globals: GET, POST, COOKIE, ENV and SERVER. There is a performance penalty
; paid for the registration of these arrays and because ENV is not as commonly
; used as the others, ENV is not recommended on productions servers. You
; can still get access to the environment variables through getenv() should you
; need to.
; Default Value: "EGPCS"
; Development Value: "GPCS"
; Production Value: "GPCS";
; http://php.net/variables-order
variables_order = "EGPCS"

この変数は，スーパーグローバル変数の解析順を示し，それぞれ，$_ENV, $_GET, $_POST, $_COOKIE, $_SERVER を生成するかを示す．