【PHP】header 发送HTTP报头函数功能详解

PHP header 发送HTTP报头函数功能详解：

函数功能：
    送出HTTP协议的头信息到用户浏览器。
    header() 函数向客户端发送原始的 HTTP 报头。

函数语法：
    header (string, replace, http_response_code)

函数返回值：整数

函数种类：网络系统

参数及说明：
    参数                 描述
    string               必需。规定要发送的报头字符串。
    replace              可选。指示该报头是否替换之前的报头，或添加第二个报头。默认是 true(替换)。false(允许相同类型的多个报头)。
    http_response_code   可选。把 HTTP 响应代码强制为指定的值。(PHP 4 以及更高版本可用)

函数内容说明：
    标头(header)是服务器以 HTTP 协议传 HTML 资料到浏览器前所送出的字符串，在标头与 HTML 文件之间尚需空一行分隔。
    在 PHP 中送回 HTML 资料前，需先传完所有的标头。

注意事项：
    传统的标头一定包含下面三种标头之一，并只能出现一次。
    Content-Type: xxxx/yyyy
    ocation: xxxx:yyyy/zzzz
    Status: nnn xxxxxx
    在新的多型标头规格 (Multipart MIME) 方可以出现二次以上。
    从 PHP 4.4 之后，该函数防止一次发送多个报头。这是对头部注入攻击的保护措施。
    认识到一点很重要，即必须在任何实际的输出被发送之前调用 header() 函数(在 PHP 4 以及更高的版本中，您可以使用输出缓存来解决此问题)。

重点注意：
    要提醒大家注意一点，所有头信息都必须在体内容之前，如果一旦有 任何输出了的话，header函数写的 头信息就没用了。
    比如，在文件最开头的php处 ，如果前面有空格或者有空行，那header函数就没用了。
    例如：
       
                    //结果出错
            //“”字符在调用 header() 之前已存在输出
            header('Location: http://www.example.com/');
        ?>
    (其实可以通过设置：output_buffer 来解决，anyway)，为什么这样，可以看看HTTP协议，很简单。

使用范例：
    1、跳转：
        header('Location: http://www.example.com/');

    2、指定内容：
        header('Content-type: application/pdf');

    3、附件：
        //指定内容为附件
        header('Content-Disposition: attachment; filename="downloaded.pdf"');
        //打开文件，并输出
        readfile('original.pdf');

    范例一：本例用来重定向用户页面到PHP的官方网站。
                Header("Location:http://www.php.net");
        exit;
        ?>

    范例二：欲让用户每次都能得到最新的资料，而不是Proxy或cache中的资料，可以使用下列的标头。
                //Date in the past
        header("Expires: Mon, 26 Jul 1997 05:00:00 GMT");
        header("Cache-Control: no-cache");
        header("Pragma: no-cache");
        ?>

    范例三：让用户的浏览器出现找不到文件的信息(404 错误)。
                header("Status:404 NotFound");
        ?>

    范例四：提供让用户下载文件的范例。提示用户保存一个生成的 PDF 文件(Content-Disposition 报头用于提供一个推荐的文件名，并强制浏览器显示保存对话框)：
                header("Content-type:application/pdf"); //文件将被称为 downloaded.pdf
        header("Content-Disposition:attachment;filename='downloaded.pdf'"); //PDF 源在 original.pdf 中
        readfile("original.pdf");
        ?>

附加知识：
        header('Content-type: application/image/pjpeg');                         //输出的类型
    header('Content-Disposition: attachment; filename="downloaded.jpg"');    //下载显示的名字，注意格式。
    readfile('my.jpg');
    //并将这个文件以前面header发送信息设定的类型输出，从而会弹出一个下载框。
    //就是把服务器上的my.jpg下载下来，下载显示和保存的名字默认是downloaded.jpg。
    ?>

    文档类型 和 服务器响应HTTP的类型：
    上面的这个可以在上传文件的类型中对应上，下面的差了点。(原文下面的是用来写在文件头上的，来确定该文件是什么类型。)

    'chm'=>'application/octet-stream',
    'ppt'=>'application/vnd.ms-powerpoint',
    'xls'=>'application/vnd.ms-excel',
    'doc'=>'application/msword',
    'exe'=>'application/octet-stream',
    'rar'=>'application/octet-stream',
    'js'=>"javascript/js",
    'css'=>"text/css",
    'hqx'=>"application/mac-binhex40",
    'bin'=>"application/octet-stream",
    'oda'=>"application/oda",
    'pdf'=>"application/pdf",
    'ai'=>"application/postsrcipt",
    'eps'=>"application/postsrcipt",
    'es'=>"application/postsrcipt",
    'rtf'=>"application/rtf",
    'mif'=>"application/x-mif",
    'csh'=>"application/x-csh",
    'dvi'=>"application/x-dvi",
    'hdf'=>"application/x-hdf",
    'nc'=>"application/x-netcdf",
    'cdf'=>"application/x-netcdf",
    'latex'=>"application/x-latex",
    'ts'=>"application/x-troll-ts",
    'src'=>"application/x-wais-source",
    'zip'=>"application/zip",
    'bcpio'=>"application/x-bcpio",
    'cpio'=>"application/x-cpio",
    'gtar'=>"application/x-gtar",
    'shar'=>"application/x-shar",
    'sv4cpio'=>"application/x-sv4cpio",
    'sv4crc'=>"application/x-sv4crc",
    'tar'=>"application/x-tar",
    'ustar'=>"application/x-ustar",
    'man'=>"application/x-troff-man",
    'sh'=>"application/x-sh",
    'tcl'=>"application/x-tcl",
    'tex'=>"application/x-tex",
    'texi'=>"application/x-texinfo",
    'texinfo'=>"application/x-texinfo",
    't'=>"application/x-troff",
    'tr'=>"application/x-troff",
    'roff'=>"application/x-troff",
    'shar'=>"application/x-shar",
    'me'=>"application/x-troll-me",
    'ts'=>"application/x-troll-ts",
    'gif'=>"image/gif",
    'jpeg'=>"image/pjpeg",
    'jpg'=>"image/pjpeg",
    'jpe'=>"image/pjpeg",
    'ras'=>"image/x-cmu-raster",
    'pbm'=>"image/x-portable-bitmap",
    'ppm'=>"image/x-portable-pixmap",
    'xbm'=>"image/x-xbitmap",
    'xwd'=>"image/x-xwindowdump",
    'ief'=>"image/ief",
    'tif'=>"image/tiff",
    'tiff'=>"image/tiff",
    'pnm'=>"image/x-portable-anymap",
    'pgm'=>"image/x-portable-graymap",
    'rgb'=>"image/x-rgb",
    'xpm'=>"image/x-xpixmap",
    'txt'=>"text/plain",
    'c'=>"text/plain",
    'cc'=>"text/plain",
    'h'=>"text/plain",
    'html'=>"text/html",
    'htm'=>"text/html",
    'htl'=>"text/html",
    'rtx'=>"text/richtext",
    'etx'=>"text/x-setext",
    'tsv'=>"text/tab-separated-values",
    'mpeg'=>"video/mpeg",
    'mpg'=>"video/mpeg",
    'mpe'=>"video/mpeg",
    'avi'=>"video/x-msvideo",
    'qt'=>"video/quicktime",
    'mov'=>"video/quicktime",
    'moov'=>"video/quicktime",
    'movie'=>"video/x-sgi-movie",
    'au'=>"audio/basic",
    'snd'=>"audio/basic",
    'wav'=>"audio/x-wav",
    'aif'=>"audio/x-aiff",
    'aiff'=>"audio/x-aiff",
    'aifc'=>"audio/x-aiff",
    'swf'=>"application/x-shockwave-flash"
    'myz'=>"application/myz"
   
    ".*"="application/octet-stream"
    ".001"="application/x-001"
    ".301"="application/x-301"
    ".323"="text/h323"
    ".906"="application/x-906"
    ".907"="drawing/907"
    ".a11"="application/x-a11"
    ".acp"="audio/x-mei-aac"
    ".ai"="application/postscript"
    ".aif"="audio/aiff"
    ".aifc"="audio/aiff"
    ".aiff"="audio/aiff"
    ".anv"="application/x-anv"
    ".asa"="text/asa"
    ".asf"="video/x-ms-asf"
    ".asp"="text/asp"
    ".asx"="video/x-ms-asf"
    ".au"="audio/basic"
    ".avi"="video/avi"
    ".awf"="application/vnd.adobe.workflow"
    ".biz"="text/xml"
    ".bmp"="application/x-bmp"
    ".bot"="application/x-bot"
    ".c4t"="application/x-c4t"
    ".c90"="application/x-c90"
    ".cal"="application/x-cals"
    ".cat"="application/vnd.ms-pki.seccat"
    ".cdf"="application/x-netcdf"
    ".cdr"="application/x-cdr"
    ".cel"="application/x-cel"
    ".cer"="application/x-x509-ca-cert"
    ".cg4"="application/x-g4"
    ".cgm"="application/x-cgm"
    ".cit"="application/x-cit"
    ".class"="java/*"
    ".cml"="text/xml"
    ".cmp"="application/x-cmp"
    ".cmx"="application/x-cmx"
    ".cot"="application/x-cot"
    ".crl"="application/pkix-crl"
    ".crt"="application/x-x509-ca-cert"
    ".csi"="application/x-csi"
    ".css"="text/css"
    ".cut"="application/x-cut"
    ".dbf"="application/x-dbf"
    ".dbm"="application/x-dbm"
    ".dbx"="application/x-dbx"
    ".dcd"="text/xml"
    ".dcx"="application/x-dcx"
    ".der"="application/x-x509-ca-cert"
    ".dgn"="application/x-dgn"
    ".dib"="application/x-dib"
    ".dll"="application/x-msdownload"
    ".doc"="application/msword"
    ".dot"="application/msword"
    ".drw"="application/x-drw"
    ".dtd"="text/xml"
    ".dwf"="Model/vnd.dwf"
    ".dwf"="application/x-dwf"
    ".dwg"="application/x-dwg"
    ".dxb"="application/x-dxb"
    ".dxf"="application/x-dxf"
    ".edn"="application/vnd.adobe.edn"
    ".emf"="application/x-emf"
    ".eml"="message/rfc822"
    ".ent"="text/xml"
    ".epi"="application/x-epi"
    ".eps"="application/x-ps"
    ".eps"="application/postscript"
    ".etd"="application/x-ebx"
    ".exe"="application/x-msdownload"
    ".fax"="image/fax"
    ".fdf"="application/vnd.fdf"
    ".fif"="application/fractals"
    ".fo"="text/xml"
    ".frm"="application/x-frm"
    ".g4"="application/x-g4"
    ".gbr"="application/x-gbr"
    ".gcd"="application/x-gcd"
    ".gif"="image/gif"
    ".gl2"="application/x-gl2"
    ".gp4"="application/x-gp4"
    ".hgl"="application/x-hgl"
    ".hmr"="application/x-hmr"
    ".hpg"="application/x-hpgl"
    ".hpl"="application/x-hpl"
    ".hqx"="application/mac-binhex40"
    ".hrf"="application/x-hrf"
    ".hta"="application/hta"
    ".htc"="text/x-component"
    ".htm"="text/html"
    ".html"="text/html"
    ".htt"="text/webviewhtml"
    ".htx"="text/html"
    ".icb"="application/x-icb"
    ".ico"="image/x-icon"
    ".ico"="application/x-ico"
    ".iff"="application/x-iff"
    ".ig4"="application/x-g4"
    ".igs"="application/x-igs"
    ".iii"="application/x-iphone"
    ".img"="application/x-img"
    ".ins"="application/x-internet-signup"
    ".isp"="application/x-internet-signup"
    ".IVF"="video/x-ivf"
    ".java"="java/*"
    ".jfif"="image/jpeg"
    ".jpe"="image/jpeg"
    ".jpe"="application/x-jpe"
    ".jpeg"="image/jpeg"
    ".jpg"="image/jpeg"
    ".jpg"="application/x-jpg"
    ".js"="application/x-javascript"
    ".jsp"="text/html"
    ".la1"="audio/x-liquid-file"
    ".lar"="application/x-laplayer-reg"
    ".latex"="application/x-latex"
    ".lavs"="audio/x-liquid-secure"
    ".lbm"="application/x-lbm"
    ".lmsff"="audio/x-la-lms"
    ".ls"="application/x-javascript"
    ".ltr"="application/x-ltr"
    ".m1v"="video/x-mpeg"
    ".m2v"="video/x-mpeg"
    ".m3u"="audio/mpegurl"
    ".m4e"="video/mpeg4"
    ".mac"="application/x-mac"
    ".man"="application/x-troff-man"
    ".math"="text/xml"
    ".mdb"="application/msaccess"
    ".mdb"="application/x-mdb"
    ".mfp"="application/x-shockwave-flash"
    ".mht"="message/rfc822"
    ".mhtml"="message/rfc822"
    ".mi"="application/x-mi"
    ".mid"="audio/mid"
    ".midi"="audio/mid"
    ".mil"="application/x-mil"
    ".mml"="text/xml"
    ".mnd"="audio/x-musicnet-download"
    ".mns"="audio/x-musicnet-stream"
    ".mocha"="application/x-javascript"
    ".movie"="video/x-sgi-movie"
    ".mp1"="audio/mp1"
    ".mp2"="audio/mp2"
    ".mp2v"="video/mpeg"
    ".mp3"="audio/mp3"
    ".mp4"="video/mpeg4"
    ".mpa"="video/x-mpg"
    ".mpd"="application/vnd.ms-project"
    ".mpe"="video/x-mpeg"
    ".mpeg"="video/mpg"
    ".mpg"="video/mpg"
    ".mpga"="audio/rn-mpeg"
    ".mpp"="application/vnd.ms-project"
    ".mps"="video/x-mpeg"
    ".mpt"="application/vnd.ms-project"
    ".mpv"="video/mpg"
    ".mpv2"="video/mpeg"
    ".mpw"="application/vnd.ms-project"
    ".mpx"="application/vnd.ms-project"
    ".mtx"="text/xml"
    ".mxp"="application/x-mmxp"
    ".net"="image/pnetvue"
    ".nrf"="application/x-nrf"
    ".nws"="message/rfc822"
    ".odc"="text/x-ms-odc"
    ".out"="application/x-out"
    ".p10"="application/pkcs10"
    ".p12"="application/x-pkcs12"
    ".p7b"="application/x-pkcs7-certificates"
    ".p7c"="application/pkcs7-mime"
    ".p7m"="application/pkcs7-mime"
    ".p7r"="application/x-pkcs7-certreqresp"
    ".p7s"="application/pkcs7-signature"
    ".pc5"="application/x-pc5"
    ".pci"="application/x-pci"
    ".pcl"="application/x-pcl"
    ".pcx"="application/x-pcx"
    ".pdf"="application/pdf"
    ".pdf"="application/pdf"
    ".pdx"="application/vnd.adobe.pdx"
    ".pfx"="application/x-pkcs12"
    ".pgl"="application/x-pgl"
    ".pic"="application/x-pic"
    ".pko"="application/vnd.ms-pki.pko"
    ".pl"="application/x-perl"
    ".plg"="text/html"
    ".pls"="audio/scpls"
    ".plt"="application/x-plt"
    ".png"="image/png"
    ".png"="application/x-png"
    ".pot"="application/vnd.ms-powerpoint"
    ".ppa"="application/vnd.ms-powerpoint"
    ".ppm"="application/x-ppm"
    ".pps"="application/vnd.ms-powerpoint"
    ".ppt"="application/vnd.ms-powerpoint"
    ".ppt"="application/x-ppt"
    ".pr"="application/x-pr"
    ".prf"="application/pics-rules"
    ".prn"="application/x-prn"
    ".prt"="application/x-prt"
    ".ps"="application/x-ps"
    ".ps"="application/postscript"
    ".ptn"="application/x-ptn"
    ".pwz"="application/vnd.ms-powerpoint"
    ".r3t"="text/vnd.rn-realtext3d"
    ".ra"="audio/vnd.rn-realaudio"
    ".ram"="audio/x-pn-realaudio"
    ".ras"="application/x-ras"
    ".rat"="application/rat-file"
    ".rdf"="text/xml"
    ".rec"="application/vnd.rn-recording"
    ".red"="application/x-red"
    ".rgb"="application/x-rgb"
    ".rjs"="application/vnd.rn-realsystem-rjs"
    ".rjt"="application/vnd.rn-realsystem-rjt"
    ".rlc"="application/x-rlc"
    ".rle"="application/x-rle"
    ".rm"="application/vnd.rn-realmedia"
    ".rmf"="application/vnd.adobe.rmf"
    ".rmi"="audio/mid"
    ".rmj"="application/vnd.rn-realsystem-rmj"
    ".rmm"="audio/x-pn-realaudio"
    ".rmp"="application/vnd.rn-rn_music_package"
    ".rms"="application/vnd.rn-realmedia-secure"
    ".rmvb"="application/vnd.rn-realmedia-vbr"
    ".rmx"="application/vnd.rn-realsystem-rmx"
    ".rnx"="application/vnd.rn-realplayer"
    ".rp"="image/vnd.rn-realpix"
    ".rpm"="audio/x-pn-realaudio-plugin"
    ".rsml"="application/vnd.rn-rsml"
    ".rt"="text/vnd.rn-realtext"
    ".rtf"="application/msword"
    ".rtf"="application/x-rtf"
    ".rv"="video/vnd.rn-realvideo"
    ".sam"="application/x-sam"
    ".sat"="application/x-sat"
    ".sdp"="application/sdp"
    ".sdw"="application/x-sdw"
    ".sit"="application/x-stuffit"
    ".slb"="application/x-slb"
    ".sld"="application/x-sld"
    ".slk"="drawing/x-slk"
    ".smi"="application/smil"
    ".smil"="application/smil"
    ".smk"="application/x-smk"
    ".snd"="audio/basic"
    ".sol"="text/plain"
    ".sor"="text/plain"
    ".spc"="application/x-pkcs7-certificates"
    ".spl"="application/futuresplash"
    ".spp"="text/xml"
    ".ssm"="application/streamingmedia"
    ".sst"="application/vnd.ms-pki.certstore"
    ".stl"="application/vnd.ms-pki.stl"
    ".stm"="text/html"
    ".sty"="application/x-sty"
    ".svg"="text/xml"
    ".swf"="application/x-shockwave-flash"
    ".tdf"="application/x-tdf"
    ".tg4"="application/x-tg4"
    ".tga"="application/x-tga"
    ".tif"="image/tiff"
    ".tif"="application/x-tif"
    ".tiff"="image/tiff"
    ".tld"="text/xml"
    ".top"="drawing/x-top"
    ".torrent"="application/x-bittorrent"
    ".tsd"="text/xml"
    ".txt"="text/plain"
    ".uin"="application/x-icq"
    ".uls"="text/iuls"
    ".vcf"="text/x-vcard"
    ".vda"="application/x-vda"
    ".vdx"="application/vnd.visio"
    ".vml"="text/xml"
    ".vpg"="application/x-vpeg005"
    ".vsd"="application/vnd.visio"
    ".vsd"="application/x-vsd"
    ".vss"="application/vnd.visio"
    ".vst"="application/vnd.visio"
    ".vst"="application/x-vst"
    ".vsw"="application/vnd.visio"
    ".vsx"="application/vnd.visio"
    ".vtx"="application/vnd.visio"
    ".vxml"="text/xml"
    ".wav"="audio/wav"
    ".wax"="audio/x-ms-wax"
    ".wb1"="application/x-wb1"
    ".wb2"="application/x-wb2"
    ".wb3"="application/x-wb3"
    ".wbmp"="image/vnd.wap.wbmp"
    ".wiz"="application/msword"
    ".wk3"="application/x-wk3"
    ".wk4"="application/x-wk4"
    ".wkq"="application/x-wkq"
    ".wks"="application/x-wks"
    ".wm"="video/x-ms-wm"
    ".wma"="audio/x-ms-wma"
    ".wmd"="application/x-ms-wmd"
    ".wmf"="application/x-wmf"
    ".wml"="text/vnd.wap.wml"
    ".wmv"="video/x-ms-wmv"
    ".wmx"="video/x-ms-wmx"
    ".wmz"="application/x-ms-wmz"
    ".wp6"="application/x-wp6"
    ".wpd"="application/x-wpd"
    ".wpg"="application/x-wpg"
    ".wpl"="application/vnd.ms-wpl"
    ".wq1"="application/x-wq1"
    ".wr1"="application/x-wr1"
    ".wri"="application/x-wri"
    ".wrk"="application/x-wrk"
    ".ws"="application/x-ws"
    ".ws2"="application/x-ws"
    ".wsc"="text/scriptlet"
    ".wsdl"="text/xml"
    ".wvx"="video/x-ms-wvx"
    ".xdp"="application/vnd.adobe.xdp"
    ".xdr"="text/xml"
    ".xfd"="application/vnd.adobe.xfd"
    ".xfdf"="application/vnd.adobe.xfdf"
    ".xhtml"="text/html"
    ".xls"="application/vnd.ms-excel"
    ".xls"="application/x-xls"
    ".xlw"="application/x-xlw"
    ".xml"="text/xml"
    ".xpl"="audio/scpls"
    ".xq"="text/xml"
    ".xql"="text/xml"
    ".xquery"="text/xml"
    ".xsd"="text/xml"
    ".xsl"="text/xml"
    ".xslt"="text/xml"
    ".xwd"="application/x-xwd"
    ".x_b"="application/x-x_b"
    ".x_t"="application/x-x_t"
    ".myz"="application/myz"