PHP - ini_set upload_max_filesize and post_max_size not working

Wonder why this does not work?

ini_set('upload_max_filesize', "16M");
ini_set('post_max_size', "16M");

These values cannot be changed during runtime, PHP must know max size before a HTTP request is recieved.

In the PHP documentation these values are marked as PHP_INI_PERDIR:

Entry can be set in php.ini, .htaccess, httpd.conf or .user.ini (since PHP 5.3)

.htaccess

php_value upload_max_filesize 16M
php_value post_max_size 16M

php.ini

post_max_size = 16M
upload_max_filesize = 16M

Also make sure your memory_limit is high enough.