有没有思忖过用PHP来做多线程操作

    //   Begin writing headers 
    header("Cache-Control:"); 
    header("Cache-Control: public"); 
    header("Content-Type: $ctype"); 

    $filespaces = str_replace("_", " ", $filename); 
    // if your filename contains underscores, replace them with spaces 

    $header='Content-Disposition: attachment; filename='.$filespaces; 
    header($header); 
    header("Accept-Ranges: bytes"); 
     
    $size = filesize($file);    
    //   check if http_range is sent by browser (or download manager)    
    if(isset($_SERVER['HTTP_RANGE'])) { 
        // if yes, download missing part       

        $seek_range = substr($_SERVER['HTTP_RANGE'] , 6); 
        $range = explode( '-', $seek_range); 
         if($range[0] > 0) { $seek_start = intval($range[0]); } 
         if($range[1] > 0) { $seek_end  =  intval($range[1]); } 
             
        header("HTTP/1.1 206 Partial Content"); 
        header("Content-Length: " . ($seek_end - $seek_start + 1)); 
        header("Content-Range: bytes $seek_start-$seek_end/$size"); 
     } else { 
        header("Content-Range: bytes 0-$seek_end/$size"); 
        header("Content-Length: $size"); 
     }    
    //open the file 
    $fp = fopen("$file","rb"); 
     
    //seek to start of missing part    
    fseek($fp,$seek_start); 
    
    //start buffered download 
    $n = 0;
    while(!feof($fp)) {        
        //reset time limit for big files 
        echo fread($fp,1024*$speed); 
     } 
    fclose($fp); 
     exit;