PHP-Laravel4.2，忽略->；其中（'；table.value'；，'；='；，$value），如果$value为空

我正在学习Laravel4.2，我对构造函数查询的雄辩性有疑问，我有以下代码

public static function filterInvoicingReport($valuesFilter){

    $fechaInicio='';
    $fechaFin='';
    $customerId='';
    $state='';
    if($valuesFilter == null)
        return;

    //obtenemos los valores de las variables dateRegisterStart y dateRegisterEnd
    if(array_key_exists('fechaInicio', $valuesFilter)&&array_key_exists('fechaFin', $valuesFilter)){
        $fechaInicio=$valuesFilter['fechaInicio'];
        $fechaFin=$valuesFilter['fechaFin'];
    }
    if(array_key_exists('customerId',$valuesFilter)){
        $customerId=$valuesFilter['customerId'];
    }
    if(array_key_exists('state',$valuesFilter)){
        $state=$valuesFilter['state'];
    }



    $sql= DB::table('invoice')
        -> select(
            'invoice.id_invoice',
            'invoice.invoice_number',
            'invoice.created_date',
            'invoice.name_seller',
            'invoice.conditions',
            'invoice.total_sale',
            'invoice.status',
            'invoice.customerId',
            'customer.name as customerName',
            'customer.identificationId as customerDNI')
        -> whereBetween(DB::raw('DATE_FORMAT(invoice.created_date,"%Y-%m-%d")'),[$fechaInicio,$fechaFin])
        ->Where('invoice.status','=',$state)
        ->Where('invoice.customerId','=',$customerId)
        -> join('customer','customer.customerId','=','invoice.customerId');
        -> get();
    return $sql;
}

是对报表的查询，问题是

$state

和

$customerId

可以为空，并且查询返回所有空

---

我想要的是，如果php中的变量为空，则只返回我的

->where

变量不为空。

将子查询添加到

where

子句：

    ->Where( function ($query) use ($state){ 
        if(!empty($state)) {
            $query->where('invoice.status','=',$state);
        } else {
            $query->whereNotNull('invoice.status');
        }
    })
    ->Where( function ($query) use ($customerId){ 
        if(!empty($customerId)) {
            $query->where('invoice.customerId','=',$customerId);
        } else {
            $query->whereNotNull('invoice.customerId');
        }
    })

---

将子查询添加到

where

子句：

    ->Where( function ($query) use ($state){ 
        if(!empty($state)) {
            $query->where('invoice.status','=',$state);
        } else {
            $query->whereNotNull('invoice.status');
        }
    })
    ->Where( function ($query) use ($customerId){ 
        if(!empty($customerId)) {
            $query->where('invoice.customerId','=',$customerId);
        } else {
            $query->whereNotNull('invoice.customerId');
        }
    })