Eloquent cannot save models with composite primary keys

[hzxie]

When defining composite primary keys then calling save on an instanced model, an exception is thrown.

ErrorException (E_UNKNOWN) 
PDO::lastInsertId() expects parameter 1 to be string, array given

And here's the declaration of Model

class ActivityAttendance extends Eloquent {
    /**
     * The database table used by the model.
     *
     * @var string
     */
    protected $table = 'activity_attendance';

    /**
     * The primary key of the table.
     * 
     * @var string
     */
    protected $primaryKey = array('activity_id', 'username');

    /**
     * The attributes of the model.
     * 
     * @var array
     */
    protected $guarded = array('activity_id', 'username', 'guests');

    /**
     * Disabled the `update_at` field in this table.
     * 
     * @var boolean
     */
    public $timestamps = false;
}

Here's the code to create new record in Controller class.

$attendance                 = new ActivityAttendance;
$attendance->activity_id    = $activityId;
$attendance->username       = $username;
$attendance->save();

[hzxie]

The issue is relative to issue #5248

[Marwelln]

This issue is well known. Eloquent doesn't support composite primary keys.

[ghost]

Its works!!!
I ignored the model of the relationship table and set "belongsToMany" in the two tables with a little details: set the two foreign key of two tables and set the name of the relationship table. The whole foreign keys will works like a composite key.

Ex:
//--------- Model "Table1": ------------//
class Table1 extends Model {
...
public function table2()
{
return $this->belongsToMany('App\Table2', 'table_relashionship', 'id_table2', 'id_table1');
}
}

//--------- Model "Table2": ------------//
class Table2 extends Model {
...
public function table1()
{
return $this->belongsToMany('App\Table1', 'table_relashionship', 'id_table1', 'id_table2');
}
}

Now the Eloquent undestand that you have a 'table_relashionship' in your database with columns 'id_table1' and 'id_table2' and you can access the data with the comand:
$table1 = Table2::find(1);
dd($table1->table2)

Its solve my problem!