How to make Max image upload file size without php.ini and .htaccess?

Hello everyone, I want to ask. Can I make max image upload file size without .htaccess and php.ini?
I have this code:

$size = $_FILE['image']['size'];

$max_upload = 800000;			
if($size >= $max_upload){ echo "Your Image file size is too big." }

But it's not working, can you help me with that? I want max image upload file size 800Kb.
Please help.
Thanks 🙂.

Thread closed; duplicate of: Strange thing with max image upload file size.. Please stop creating multiple threads for the same issue.