A simple trait for Eloquent models that provides convenience filters and methods for checking ownership

OwnedModelTrait.php

<?php

namespace App\Traits;

use App\User;

/**
 * A model that is owned by a user
 */
trait OwnedModelTrait
{
    /**
     * Get the owner of the model
     *
     * @return \Illuminate\Database\Eloquent\Relations\BelongsTo
     */
    public function user()
    {
        return $this->belongsTo("App\User");
    }

    /**
     * Check if the model is owned by the given user. Does not check for existence of user
     *
     * @param \App\User|int $user The user instance or user ID
     *
     * @throws \InvalidArgumentException If the provided argument is neither a user ID
     *         nor a User instance
     *
     * @return bool
     */
    public function isOwnedBy($user): bool
    {
        if (! self::isUserOrUserId($user)) {
            throw new \InvalidArgumentException(sprintf(
                "isOwnedBy() expected User instance or ID, got %s",
                is_object($user) ? get_class($user) : gettype($user)
            ));
        }

        return ($this->user_id === (is_int($user) ? $user : $user->id));
    }

    /**
     * Filter models by owner. Does not check for existence of user
     *
     * @throws \InvalidArgumentException If the provided argument is neither a
     *         valid user ID (greater than 0) nor a User instance
     *
     * @return \Illuminate\Database\Eloquent\Builder
     */
    public function scopeOwnedBy($query, $user)
    {
        if (! self::isUserOrUserId($user)) {
            throw new \InvalidArgumentException(sprintf(
                "scopeOwnedBy() expected User instance or ID, got %s",
                is_object($user) ? get_class($user) : gettype($user)
            ));
        }

        return $query->where("user_id", "=", is_int($user) ? $user : $user->id);
    }

    /**
     * Utility method to check if a given argument is a user instance or a user ID
     *
     * @param mixed $user The object to check
     *
     * @return bool True if the parameter is a integer greater than 0 or a User instance
     */
    private static function isUserOrUserId($user): bool
    {
        return ($user instanceof User || (is_int($user) && $user > 0));
    }
}