php clear echo messages

1<?php
2
3ob_start();
4echo 'a';
5print 'b';
6
7// some statement that removes all printed/echoed items
8ob_end_clean();
9
10echo 'c';
11
12// the final output is equal to 'c', not 'abc'
13
14?>
15// https://stackoverflow.com/questions/1057986/how-to-clear-previously-echoed-items-in-php