if you want to backup and restore your big MySQL databases you need better solution than phpmyadmin

So here we go;

To dump all databases to a file:

$ mysqldump -u dbuser -pdbpass --all-databases > all-databases.sql

To dump a single database to a file:

$ mysqldump -u dbuser -pdbpass somedb > somedb.sql

Dump InnoDB in a single transaction:

$ mysqldump -u dbuser -pdbpass --single-transaction somedb > somedb.sql

To restore:

$ mysql -u dbuser -pdbpass somedb < somedb.sql