PHP获取网站域名跟地址的代码

PHP获取网站域名和地址的代码
http://www.jb51.net/article/15514.htm

function PMA_getenv($var_name) {if (isset ( $_SERVER [$var_name] )) {return $_SERVER [$var_name];} elseif (isset ( $_ENV [$var_name] )) {return $_ENV [$var_name];} elseif (getenv ( $var_name )) {return getenv ( $var_name );} elseif (function_exists ( 'apache_getenv' ) && apache_getenv ( $var_name, true )) {return apache_getenv ( $var_name, true );}return '';}if (empty ( $HTTP_HOST )) {if (PMA_getenv ( 'HTTP_HOST' )) {$HTTP_HOST = PMA_getenv ( 'HTTP_HOST' );} else {$HTTP_HOST = '';}}//echo htmlspecialchars($HTTP_HOST );