Why does ob_get_clean wipe memory without starting the buffer with ob_start()?

Question

I was one day doing some tests, analyzing how functions influence memory usage, and, by chance, called the function ob_get_clean(). I noticed that the function call "decreased" the memory size used by php.

With ob_start() I noticed earlier that the use of memory increased, as expected, because it stores the output in a buffer.

Now I don’t understand why ob_get_clean() "cleaned" some value of buffer, decreasing memory, and ob_start() was not called anywhere in the code.

Below follows the results I obtained:

<?php
echo memory_get_usage(); //122224
?>

<?php
ob_get_clean();
echo memory_get_usage(); //113992
?>

Does anyone know why when calling ob_get_clean() memory has diminished?

Is there any configuration in php.ini that starts the buffer automatically or something like that?

Answer 1

Yes, there is.

In his php.ini how the option is configured output_buffering ?

output_buffering=On

Activates the automatic output buffer.

You can disable it:

output_buffering=Off

or specify buffer size:

output_buffering=4096

See more: Output Buffering in the PHP manual