Mastering PHP 7

Output buffering

Output buffering is a PHP mechanism that controls the output of a script. Imagine we write down echo 'test'; within our PHP script and do not see anything on screen. How is that possible? The answer is output buffering.

The following piece of code is a simple example of output buffering:

<?phpob_start();sleep(2);echo 'Chunk#1' . PHP_EOL;sleep(3);ob_end_flush();ob_start();echo 'Chunk#2' . PHP_EOL;sleep(5);ob_end_clean();ob_start();echo 'Chunk#3' . PHP_EOL;ob_end_flush();ob_start();sleep(5);echo 'Chunk#4' . PHP_EOL;//Chunk#1//Chunk#3//Chunk#4

When executed within the CLI environment, we will first see Chunk#1 come out after a few seconds, then a few seconds after, we will see Chunk#3 come out, and, finally, a few more seconds ...