What is relationship count condition in WhereHas Laravel

Question

I am having a difficulty understanding the relationship count condition in WhereHas. The docs page does not have discussion about it but API page talks about it. Quote from API.

Builder|Builder whereHas(string $relation, Closure $callback, string $operator = '>=', int $count = 1)

Add a relationship count condition to the query with where clauses.

Example

A Resource Model has Many to Many relation to ResourceCategory

public function categories()
{
    return $this->belongsToMany('ResourceCategory', 'resource_category_mapping');
}

Relationship condition in Has

The relationship condition in Has is working as expected.

Resource::has('categories', '>', 1)->get()
//this return all resources which have more than one catgories

Relationship condition in WhereHas

The relationship condition in WhereHas is not working as expected. I am sure I have misunderstood it.

Resource::whereHas('categories', function ( $query){
            $query->whereIn('resource_category_id', [1, 2, 4]);
        }, '>', 1)->get()

The above code should return resources which whose categories belong to either of [1, 2, 4] and the resource has more than one categories. But it is not.

Question

Kindly explain the relationship condition in WhereHas, may be providing an example would be much helpful.

Answer 1

Normally, whereHas() checks if your model has at least one related model. You can set $count to some higher value to increase the count to Nand fetch only the models that have at least N related models.

In your case, calling

Resource::has('categories', '>', 2)->get();

will return only those Resources that have at least 2 related categories.