Trait that enables a Eloquent model to have Composite Keys.

HasCompositePrimaryKey.php

<?php

namespace App\Traits;

use RuntimeException;

trait HasCompositePrimaryKey
{
    public function getIncrementing(): bool
    {
        return false;
    }

    protected function setKeysForSaveQuery($query)
    {
        foreach ($this->getKeyName() as $key) {
            if (isset($this->$key)) {
                $query->where($key, '=', $this->$key);
            }
            else {
                throw new RuntimeException(__METHOD__ . 'Missing part of the primary key: ' . $key);
            }
        }

        return $query;
    }

    /**
     * Execute a query for a single record by ID.
     *
     * @param  array  $ids Array of keys, like [column => value].
     * @param  array  $columns
     * @return mixed|static
     */
    public static function find($ids, $columns = ['*'])
    {
        $me = new self;
        $query = $me->newQuery();
        foreach ($me->getKeyName() as $key) {
            $query->where($key, '=', $ids[$key]);
        }
        return $query->first($columns);
    }

    /**
     * Get an attribute from the model.
     *
     * @param  string|array  $key
     * @return mixed
     */
    public function getAttribute($key)
    {
        if (!$key || is_array($key)) {
            return;
        }

        // If the attribute exists in the attribute array or has a "get" mutator we will
        // get the attribute's value. Otherwise, we will proceed as if the developers
        // are asking for a relationship's value. This covers both types of values.
        if (array_key_exists($key, $this->attributes) ||
            array_key_exists($key, $this->casts) ||
            $this->hasGetMutator($key) ||
            $this->isClassCastable($key)) {
            return $this->getAttributeValue($key);
        }

        // Here we will determine if the model base class itself contains this given key
        // since we don't want to treat any of those methods as relationships because
        // they are all intended as helper methods and none of these are relations.
        if (method_exists(self::class, $key)) {
            return;
        }

        return $this->getRelationValue($key);
    }
}