Imagine your building a multi-tenancy application, in your controller your using a Contacts model every single time you pull a query out it needs constraining to the current tenant like this:
$contacts = Contact::where('tenant_id', session('tenant_id')->paginate();
Using a global scope would mean the constraint could be applied to all your queries automatically.
In your model using the static boot method. Add a static addGlobalScope the first param is the name of the scope and the second is a closure which is type hinted to use $builder.
Inside the closure add the where constraint. In this case I'm saying where the tenant_id matches a tenant_id stored in a session.
protected static function boot()
{
parent::boot();
//apply condition to all queries
static::addGlobalScope('tenent', function (Builder $builder) {
$builder->where('tenant_id', session('tenant_id'));
});
}
Import the builder
//import Builder
use Illuminate\Database\Eloquent\Builder;
Now this will be applied automatically to your queries so pull all contacts is now simplified to this:
$contacts = Contact::paginate();