php头部返回状态码：

// ok 正常访问
header('HTTP/1.1 200 OK');
//通知浏览器 页面不存在
header('HTTP/1.1 404 Not Found');
//设置地址被永久的重定向 301
header('HTTP/1.1 301 Moved Permanently');
//跳转到一个新的地址
header('Location: http://www.baidu.com/');
//延迟转向 也就是隔几秒跳转
header('Refresh: 10; url=http://www.baidu.com/');
//修改 X-Powered-By信息
header('X-Powered-By: PHP/6.0.0');
//文档语言
header('Content-language: en');
//设置内容长度
header('Content-Length: 1234');
//告诉浏览器最后一次修改时间
header('Last-Modified: '.gmdate('D, d M Y H:i:s', $time).' GMT');
//告诉浏览器文档内容没有发生改变
header('HTTP/1.1 304 Not Modified');

返回文档类型：

header('Content-Type: text/html; charset=utf-8'); //网页编码
header('Content-Type: text/plain'); //纯文本格式
header('Content-Type: image/jpeg'); //JPG、JPEG
header('Content-Type: application/zip'); // ZIP文件
header('Content-Type: application/pdf'); // PDF文件
header('Content-Type: audio/mpeg'); // 音频文件
header('Content-type: text/css; charset=utf-8'); //css文件
header('Content-type: text/javascript; charset=utf-8'); //js文件
header('Content-type: application/json; charset=utf-8'); //json
header('Content-type: application/pdf'); //pdf
header('Content-type: text/xml; charset=utf-8'); //xml
header('Content-Type: application/x-shockw**e-flash'); //Flash动画

声明一个下载的文件：

header('Content-Type: application/octet-stream');
header('Content-Disposition: attachment; filename="XXX.zip"');
header('Content-Transfer-Encoding: binary');
readfile('test.zip');//读取文件下载

对当前文档禁用缓存：

header('Cache-Control: no-cache, no-store, max-age=0, must-revalidate');
header('Expires: Mon, 26 Jul 1997 05:00:00 GMT');

显示一个需要验证的登陆对话框：

header('HTTP/1.1 401 Unauthorized');
header('WWW-Authenticate: Basic realm="Top Secret"');

声明一个需要下载的xls文件：

header('Content-Disposition: attachment; filename=ithhc.xlsx');
header('Content-Type: application/vnd.openxmlformats-officedocument.spreadsheetml.sheet');
header('Content-Length: '.filesize('./test.xls'));
header('Content-Transfer-Encoding: binary');
header('Cache-Control: must-revalidate');
header('Pragma: public');
readfile('./test.xls');

其它返回头：

header('Content-Length: $size'); //告诉浏览器数据长度,浏览器接收到此长度数据后就不再接收数据
header('Connection: Close'); //告诉浏览器关闭当前连接,即为短连接