php
<code> if (isset($_SERVER['SERVER_PORT'])) { $port = ':' . $_SERVER['SERVER_PORT']; if ((':80' == $port && 'http://' == $protocol) || (':443' == $port && ' https://' == $protocol)) { $port = ''; } }</code>其中
<code> if ((':80' == $port && 'http://' == $protocol) || (':443' == $port && 'https://' == $protocol)) { $port = ''; }</code>这段代码的意思作用是什么？ 如果条件成立，为什么要把$port 设置为空？
整个函数的代码：
<code> function get_domain() { /* 协议 */ $protocol = $this->http(); /* 域名或IP地址 */ if (isset($_SERVER['HTTP_X_FORWARDED_HOST'])) { $host = $_SERVER['HTTP_X_FORWARDED_HOST']; } elseif (isset($_SERVER['HTTP_HOST'])) { $host = $_SERVER['HTTP_HOST']; } else { /* 端口 */ if (isset($_SERVER['SERVER_PORT'])) { $port = ':' . $_SERVER['SERVER_PORT']; if ((':80' == $port && 'http://' == $protocol) || (':443' == $port && 'https://' == $protocol)) { $port = ''; } } else { $port = ''; } if (isset($_SERVER['SERVER_NAME'])) { $host = $_SERVER['SERVER_NAME'] . $port; } elseif (isset($_SERVER['SERVER_ADDR'])) { $host = $_SERVER['SERVER_ADDR'] . $port; } } return $protocol . $host; }</code>
