详解如何让PHP实现断点续传

$fname = './05e58c19552bb26b158f6621a6650899'; 
$fp = fopen($fname,'rb'); 
$fsize = filesize($fname); 
if (isset($_SERVER['HTTP_RANGE']) && ($_SERVER['HTTP_RANGE'] != "") && preg_match("/^bytes=([0-9]+)-$/i", $_SERVER['HTTP_RANGE'], $match) && ($match[1] < $fsize)) { 
$start = $match[1]; 
} else { 
$start = 0; 
} 
@header("Cache-control: public"); 
@header("Pragma: public"); 
if ($start > 0) { 
fseek($fp, $start); 
Header("HTTP/1.1 206 Partial Content"); 
Header("Content-Length: " . ($fsize - $start)); 
Header("Content-Ranges: bytes" . $start . "-" . ($fsize - 1) . "/" . $fsize); 
} else { 
header("Content-Length: $fsize"); 
Header("Accept-Ranges: bytes"); 
} 
@header("Content-Type: application/octet-stream"); 
@header("Content-Disposition: attachment;filename=1.rm"); 
fpassthru($fp);

$range = 0; 
if($readmod == 4) { 
dheader('Accept-Ranges: bytes'); 
if(!emptyempty($_SERVER['HTTP_RANGE'])) { 
list($range) = explode('-',(str_replace('bytes=', '', $_SERVER['HTTP_RANGE']))); 
$rangesize = ($filesize - $range) > 0 ? ($filesize - $range) : 0; 
dheader('Content-Length: '.$rangesize); 
dheader('HTTP/1.1 206 Partial Content'); 
dheader('Content-Range: bytes='.$range.'-'.($filesize-1).'/'.($filesize)); 
} 
}