if you have an upload limit for your site or you need to upload a larg sql file with phpmyadmin or you want to upload larg images you can extend it with this command. Just add it to your .htaccess file.
php_value upload_max_filesize 42M php_value post_max_size 42M
or keep it permanent and add it to your php.ini by edit the followings:
memory_limit = 42M upload_max_filesize = 24M post_max_size = 42M