controller：

$subject = Db::name('subject')->select();
$subject = addWebSiteUrl($subject, ['image', 'expression']);

处理前查询结果：

{
	"id": 1,
	"module": 179,
	"group": 180,
	"image": "/uploads/images/20191126/8ff0117b29674204ca282ec6c0b41dae.png",
	"expression": "/uploads/images/20191126/e64d1eee738b6dd632a33515567975f9.png",
	"anwser": "1",
	"key": "w"
},
{
	"id": 2,
	"module": 179,
	"group": 180,
	"image": "/uploads/images/20191202/a8587980dfde573f85fb1775f8a3b4cd.jpeg",
	"expression": "/uploads/images/20191202/ba3042f2170350a9b4542840361e7074.jpeg",
	"anwser": "4",
	"key": "f"
}

common.php

/**
 * @param array $array 要处理的数组
 * @param array $fields 要处理的字段名
 * @return array
 */
function addWebSiteUrl($array = [], $fields = [])
{
    if (!empty($array) && !empty($fields)) {
        foreach ($array as &$v1) {
            foreach ($fields as &$v2) {
                $v1[$v2] = "http://www.123.123".$v1[$v2];
            }
        }
        return $array;
    }
}

处理后查询结果：

{
	"id": 1,
	"module": 179,
	"group": 180,
	"image": "http://www.123.123/uploads/images/20191126/8ff0117b29674204ca282ec6c0b41dae.png",
	"expression": "http://www.123.123/uploads/images/20191126/e64d1eee738b6dd632a33515567975f9.png",
	"anwser": "1",
	"key": "w"
},
{
	"id": 2,
	"module": 179,
	"group": 180,
	"image": "http://www.123.123/uploads/images/20191202/a8587980dfde573f85fb1775f8a3b4cd.jpeg",
	"expression": "http://www.123.123/uploads/images/20191202/ba3042f2170350a9b4542840361e7074.jpeg",
	"anwser": "4",
	"key": "f"
}