A default installation of PHP and Apache on a Ubuntu 12.04 will set a maximum upload limit of 2MB. Quite often you will want to increase this to a larger size. How high you set this limit will depend on your requirements.
This howto guide will step you through the process to increase the PHP upload limit.
Increasing PHP upload limit:
Edit the /etc/php5/apache2/php.ini file in an editor.
$ sudo nano /etc/php5/apache2/php.ini
search for the following line:
upload_max_filesize = 2M
Change the 2M setting to suit your requirements. I’ll use 10MB in this example.
upload_max_filesize = 10M
Save the file and exit the editor.
Restart Apache to make the changes take effect:
$ sudo service apache2 restart
You should now be able to upload files up to 10MB in size to a PHP script on your site.