Send a file to the client via PHP in a streaming way

Sending a file to the client via PHP in a streaming manner

Previously, under ASP, similar functions were implemented through BASP21. Now the PHP version is organized here.

There are several possible requirements that can be achieved through the techniques used in the following code:

1, on the basis of a template, customized for customers to download.

2, some browser itself can represent the type of file (such as TXT file), you can change the header information Content-type to the header ("Content-type:application/force-download"), to force the download.

3, for some dynamic generated files, such as txt/csv files, temporary files are deleted in time

