Change default primary key in Eloquent

Yes

class User extends Eloquent {

    protected $primaryKey = 'admin_id';

}

If you are wanting to use a composite key (a string)

You need to make sure you set public $incrementing = false otherwise laravel will cast the field to an Integer, giving 0

class User extends Model {

    protected $primaryKey = 'my_string_key';
    public $incrementing = false;

}

class User extends Eloquent {

    protected $primarykey = 'admin_id';

}

but

class User extends Eloquent {

    protected $primaryKey = 'admin_id';

}

note the letter K (capital) on the variable $primaryKey

The primary key variable is case sensitive and must be $primaryKey to work.

Example:

protected $primaryKey = 'your_primary_key_id';

Example within a Model class:

class User extends Eloquent {

    protected $primaryKey = 'your_primary_key_id';

}

class User extends Eloquent {

    protected $primaryKey = 'admin_id';

}

As per Laravel documentation :

Eloquent will also assume that each table has a primary key column named id. You may define a $primaryKey property to override this convention.

In addition, Eloquent assumes that the primary key is an incrementing integer value, which means that by default the primary key will be cast to an int automatically. If you wish to use a non-incrementing or a non-numeric primary key you must set the public $incrementing property on your model to false.