It is session-based, when set the way you did in your question.
https://dev.mysql.com/doc/refman/5.7/en/server-system-variables.html
According to this, FOREIGN_KEY_CHECKS
is “Both” for scope. This means it can be set for session:
SET FOREIGN_KEY_CHECKS=0;
or globally:
SET GLOBAL FOREIGN_KEY_CHECKS=0;