I have mulutiselect option enabled in select html code, my frontend look like this: 
For example if user unselect some option and select other how can I update it in database, any idea?
I have mulutiselect option enabled in select html code, my frontend look like this: 
For example if user unselect some option and select other how can I update it in database, any idea?
If you have ManyToMany relationships between say Group and Project you can use sync() method to maintain association as below,
$group->projects()->sync([$projId1, $projId2]);
Above will remove all previous association between current group($group) and projects and associates newly supplied projects i.e. $projId1, $projId2.
If you want to maintain previous associations pass false as a second argument in sync() as below,
$group->projects()->sync([$projId1, $projId2], false);
Above code will maintain previous Group and Project association and will also associate passed projects.