ERROR 2006 (HY000) at line ##: MySQL server has gone away

 MySQL server has gone away : Error while uploading sql file in phpmyadmin

1) Open file my.cnf 
xampp : /opt/lampp/etc/my.cnf
apache2 (Debian) : /etc/mysql/my.cnf 
httpd (RHEL, CentOS) : /etc/my.cnf

2) Set value max_allowed_packet=128M under attribute [mysqld] 
    If parameter is not there, add it under attribute [mysqld] .

[mysqld]
max_allowed_packet=128M

3) Restart mysql.