Step 1: Go to the directory: “/etc/php5/apache2”, open the php.ini and search for “upload_max_filesize”, then change to 512M, 1024M, 2048M…etc… Moreover, search for “memory_limit” and change it into 512M. 

Step 2: Go to the directory: “/etc/mysql”, open my.cnf and change “max_allowed_packet” from 16M into 32M 

Step 3: Reboot the system.