Here is my noted about error in PHP, and how to solve it. Maybe it will be update if I have any error and solve the error in the future. I will write the error by the date and number. Hopefully can help anyone need. Thanks.
1. warning cannot modify header information - headers already sent by (output started at php)
That warning, I get in some work, but, when I run in locally, the error has gone. But not in Hosting/online.
How to solve? Just give the ob_start(); function in the second line after <?php tag. Like below
<?php
ob_start();
//some command
//some command
?>
2. Notice: A non well formed numeric value encountered in