PHP large file download program [http cache negotiation, Etag mark, breakpoint resume]_PHP tutorial

002 $file_path = './download/download_cn.rar';

003

004 //How to use

005 downFile($file_path);

006

007 // Server file path, download file name (default is server file name), whether to allow user download method (default optional) , speed limit (default automatic), file type (default all)

008 function downFile($fileName, $fancyName = '', $forceDownload = true, $speedLimit = 0, $contentType = '') {

009 if (!is_readable($fileName))

010 {

011 header("HTTP/1.1 404 Not Found");

012 return false; ]; 

017                                                       ']);

019 $etag = '"' . $md5 . '-' . crc32($md5) . '"';

020

021 header ('Last-Modified: ' . gmdate("D, d M Y H:i:s", $lastModified) . ' GMT');

022 header("ETag: $etag");

023 

024 if (isset($_SERVER['HTTP_IF_MODIFIED_SINCE']) && strtotime($_SERVER['HTTP_IF_MODIFIED_SINCE']) >= $lastModified) 

025 {

026 header("HTTP/1.1 304 Not Modified");

027 return true;

028 }

029

0 30 if (isset($_SERVER['HTTP_IF_UNMODIFIED_SINCE']) && strtotime($_SERVER['HTTP_IF_UNMODIFIED_SINCE']) < $lastModified)

031 {

032 header("HTTP/1.1 304 Not Modified");

033 return true;

034 }

035 & $ _SERVER['HTTP_IF_NONE_MATCH'] == $etag)

037 {

038 header("HTTP/1.1 304 Not Modified");

039 return true;

040 }  

041                                                                                                                                              $ fileName); $ contentType = 'application/octet-stream';

050 }

051

054 $contentLength = $fileSize;

055 $isPartial = false;

056

057 if (isset($_SERVER['HTTP_RANGE'] ))

058 {

059 if (preg_match('/^bytes=(d*)-(d*)$/', $_SERVER['HTTP_RANGE'], $matches) )                                                                                                     063 

064 if ($startPos == '' && $endPos == '')

065 {

066                 return false;  

067             }  

068     

069             if ($startPos == '')  

070             {  

071                 $startPos = $fileSize - $endPos;  

072                 $endPos = $fileSize - 1;  

073             }  

074             else if ($endPos == '')  

075             {  

076                 $endPos = $fileSize - 1;  

077             }  

078     

079             $startPos = $startPos < 0 ? 0 : $startPos;  

080             $endPos = $endPos > $fileSize - 1 ? $fileSize - 1 : $endPos;  

081     

082             $length = $endPos - $startPos + 1;  

083     

084             if ($length < 0)  

085             {  

086                 return false;  

087             }  

088     

089             $contentLength = $length;  

090             $isPartial = true;  

091         }  

092     }  

093     

094     // send headers  

095     if ($isPartial)  

096     {  

097         header('HTTP/1.1 206 Partial Content');  

098         header("Content-Range: bytes $startPos-$endPos/$fileSize");  

099     

100     }  

101     else 

102     {  

103         header("HTTP/1.1 200 OK");  

104         $startPos = 0;  

105         $endPos = $contentLength - 1;  

106     }  

107     

108     header('Pragma: cache');  

109     header('Cache-Control: public, must-revalidate, max-age=0');  

110     header('Accept-Ranges: bytes');  

111     header('Content-type: ' . $contentType);  

112     header('Content-Length: ' . $contentLength);  

113     

114     if ($forceDownload)  

115     {  

116         header('Content-Disposition: attachment; filename="' . rawurlencode($fancyName). '"');  

117     }  

118     

119     header("Content-Transfer-Encoding: binary");  

120     

121     $bufferSize = 2048;  

122     

123     if ($speedLimit != 0)  

124     {  

125         $packetTime = floor($bufferSize * 1000000 / $speedLimit);  

126     }  

127     

128     $bytesSent = 0;  

129     $fp = fopen($fileName, "rb");  

130     fseek($fp, $startPos);  

131     while ($bytesSent < $contentLength && !feof($fp) && connection_status() == 0 )  

132     {  

133         if ($speedLimit != 0)  

134         {  

135             list($usec, $sec) = explode(" ", microtime());  

136             $outputTimeStart = ((float)$usec + (float)$sec);  

137         }  

138     

139         $readBufferSize = $contentLength - $bytesSent < $bufferSize ? $contentLength - $bytesSent : $bufferSize;  

140         $buffer = fread($fp, $readBufferSize);  

141     

142         echo $buffer;  

143     

144         ob_flush();  

145         flush();  

146     

147         $bytesSent += $readBufferSize;  

148     

149         if ($speedLimit != 0)  

150         {  

151             list($usec, $sec) = explode(" ", microtime());  

152             $outputTimeEnd = ((float)$usec + (float)$sec);  

153     

154             $useTime = ((float) $outputTimeEnd - (float) $outputTimeStart) * 1000000;  

155             $sleepTime = round($packetTime - $useTime);  

156             if ($sleepTime > 0)  

157             {  

158                 usleep($sleepTime);  

159             }  

160         }  

161     }  

162     return true;  

163 }  

164 ?>