is_ssl() : HTTPSプロトコルかどうかを返す - Qiita

<?php /** * Determine if the protocol is HTTPS. * @return bool */ public function is_ssl() { if ( isset($_SERVER['HTTPS']) === true ) // Apache { return ( $_SERVER['HTTPS'] === 'on' or $_SERVER['HTTPS'] === '1' ); } elseif ( isset($_SERVER['SSL']) === true ) // IIS { return ( $_SERVER['SSL'] === 'on' ); } elseif ( isset($_SERVER['HTTP_X_FORWARDED_PROTO']) === true ) // Reverse proxy { return ( str