An Eloquent Scope that extends the builder with private/protected methods.

ExtendableScope.php

<?php

namespace App\Scopes;

use Illuminate\Database\Eloquent\Builder;
use Illuminate\Database\Eloquent\Model;
use Illuminate\Database\Eloquent\Scope;
use Illuminate\Support\Collection;
use ReflectionClass
use SplFixedArray;

class ExtendableScope implements Scope
{
    /**
     * List of (fixed) methods for the current scope.
     *
     * @var \SplFixedArray(int, \ReflectionMethod)
     */
    protected static SplFixedArray $methods;

    /**
     * Apply the scope to a given Eloquent query builder.
     *
     * @param  \Illuminate\Database\Eloquent\Builder  $builder
     * @param  \Illuminate\Database\Eloquent\Model  $model
     * @return void
     */
    public function apply(Builder $builder, Model $model): void
    {
        // ...
    }

    /**
     * Extend the Eloquent Query Builder instance with macros.
     *
     * @param  \Illuminate\Database\Eloquent\Builder  $builder
     * @return void
     */
    public function extend(Builder $builder): void
    {
        static::$methods ??= SplFixedArray::fromArray(
            Collection::make((new ReflectionClass($this))->getMethods())
                ->filter(fn($method) => !$method->isPublic() && !$method->isStatic())
                ->toArray()
        );
        
        foreach (static::$methods) as $method) {
            $builder->macro($method, $method->getClosure());
        }
    }

    /**
     * This is an example method that will be added to query builder.
     *
     * @example Model::where('adult', true)->age(28);
     *
     * @param  \Illuminate\Database\Eloquent\Builder  $query
     * @param  int  $age
     * @return \Illuminate\Database\Eloquent\Builder
     */
    protected function age(Builder $query, int $age): Builder
    {
        return $query->where('age', $age);
    }
}