VGirol / JsonApi

src/macro/relation.php

<?php

use Illuminate\Database\Eloquent\Relations\BelongsToMany;
use Illuminate\Database\Eloquent\Relations\HasMany;
use Illuminate\Database\Eloquent\Relations\HasManyThrough;
use Illuminate\Database\Eloquent\Relations\MorphMany;
use Illuminate\Database\Eloquent\Relations\MorphToMany;
use Illuminate\Database\Eloquent\Relations\Relation;

Relation::macro(

The method macro() does not exist on Illuminate\Database\Eloquent\Relations\Relation. It seems like you code against a sub-type of Illuminate\Database\Eloquent\Relations\Relation such as Illuminate\Database\Eloquent\Relations\MorphTo.

    'isToMany',
    function (): bool {
        return is_a($this, HasMany::class) || is_a($this, BelongsToMany::class)

The variable $this seems to be never defined.

            || is_a($this, MorphMany::class) || is_a($this, MorphToMany::class)
            || is_a($this, HasManyThrough::class);
    }
);