if what you need to do is specific only for 1 or 2 pages i suggest to use set_time_limit so it did not affect the whole application.
set_time_limit(some_values);
but ofcourse these 2 values (post_max_size & upload_max_filesize) are subject to investigate.
you either can set it via ini_set function
ini_set('post_max_size','20M');
ini_set('upload_max_filesize','2M');
or directly in php.ini file like response above by Hannes, or even set it iin .htaccess like below
php_value upload_max_filesize 2M
php_value post_max_size 20M