ob_get_length（）方法有什么用？

Question

i know those methods related to output buffering:

<?php
ob_start();

// some code

ob_end_flush();
ob_end_clean();

but i can't figure out why will i need the length of the output buffer. there is one question here is SOF about measuring the bandwidth of the user ,although that calculation will need to measure pictures and other files which is not addressed.

i did check the PHP manual and the "why" is not there.

Answer 1

Answering "why to use it". In order to answer this, we must first understand why we need to use ob_start. Usually it is used for two purpose:

1. When we want to send HTTP headers, but we are not sure, that there is no rendering before(the first output will trigger header sending, so if you use, echo for example, before header, the later won't work)
2. When we want to send our output by chunks for performance. (your code can be written with a lot of echo or print, and usually they outputing only small data, so you are sending small portions of data back to browser, which is affecting performance.)

So now you can start to guess, why we need to use ob_get_length(). For example: i want to send my output by large chunks, so i am enabling output buffering and with the help of ob_get_lengthi can control how many data i can write to buffer, before sending it.