While you can set the PHP variable "upload_max_filesize" for only your account, our servers will remain at a default value. In order to change it for your script, you have to create or edit a ".htaccess" file in your scripts directory. Add the following in this file:
php_value upload_max_filesize xM
You may also need to add the PHP variable "post_max_size", to the same value as above, for PHP to accept a POST of that size:
php_value post_max_size xM
Where x is the value needed. Please keep this value to a reasonable level.