Yesterday, I wrote a plugin and uploaded it to my website. I activated it and it activated successfully.

But when I deactivated it, the page turns blank.

On returning to the WordPress admin page, the plugin was successfully deactivated.

I was also getting problems when I added custom field.

The cause ?

A blank line at the beginning of my plugin file.

Deleting the blank line and letting the first line be <?php solved the problem.