Modifying the php.ini file

These instructions show you how to change the file upload size by editing your php.ini file.

For the most part these instructions amount to the following. In the file /etc/php5/apache2/php.ini you need to change “post_max_size”, “upload_max_filesize” and “max_execution_time” to values that suit your needs using whatever editor you are used to.

Below are some line by line instructions for various installations of Moodle

Source: File upload size – MoodleDocs