返回文件顶部插入的字符（换行符）会破坏文件PHP吗？

Question

I have a function that returns an image from a database, the image is 100% fine in the database however when it is sent to the browser a newline (return) character is inserted in the very beginning and it corrupts the file.

The code to return the file is:

//if(ob_get_length() > 0)
            //{
                //ob_clean();
            //}

Commented the above out as when it is uncommented it doesn't even let the browser download the file.

function header_file($data, $file_data)
            {
                $last_modified = gmdate('D, d M Y H:i:s', $file_data['unix_last_modified_time'])." GMT";

                // update the accessed record
                $GLOBALS['db']->query("update file_uploads set file_upload_accessed_count = file_upload_accessed_count + 1 where file_upload_id = '".$GLOBALS['id']."'");

                // if browser question if it's up to date
                if (isset($_SERVER['HTTP_IF_MODIFIED_SINCE']))
                {
                    // parse header
                    $if_modified_since = preg_replace('/;.*$/', '', $_SERVER['HTTP_IF_MODIFIED_SINCE']);

                    if ($if_modified_since == $last_modified)
                    {
                        // the browser's cache is still up to date
                        header("HTTP/1.0 304 Not Modified");
                        header("Cache-Control: max-age=86400, must-revalidate");
                        exit;
                    }
                }

                header("Cache-Control: max-age=86400, must-revalidate");
                header("Last-Modified: ".$last_modified);
                header("Content-Type: ".$file_data['file_upload_type']);

                if($file_data['file_upload_type'] == 'application/x-shockwave-flash')
                    header("Content-Disposition: inline; filename=\"".str_replace(' ','_',$file_data['file_upload_name'])."\"");
                else
                    header("Content-Disposition: attachment; filename=\"".str_replace(' ','_',$file_data['file_upload_name'])."\"");

                // send data to output
                echo $data;
                exit;
            }

Related Questions: Corrupted File from PHP Header File returned from database? https://stackoverflow.com/questions/19768650/zend-caching-of-images-gives-problems-once-the-site-goes-down-for-a-while

Answer 1

I would do the following. You have an extra space somewhere in your PHP file.
It can be a bit tricky to find, so start putting some

echo "here" 

in your code to see if this newline is found before or after the echo. Keep moving he echo statement up or down the file until you can see where it is (it might be in an include file, so you will have to track it down.

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