解决Laravel表单提交默认将空值转为null

在Laravel中，使用$request->inptu('field')，获取参数值为空的时候，输出的值为null

name: peak
province: 北京市
city: 崇文区
mobile: 18000000000
address: 你猜猜看
zip:

获取 zip 的值

1 2	$zip = $request->input('zip', ''); dd($zip);

发现 zip 并没有输出 ''，而是输出 null

原来，在 Illuminate/Foundation/Http 组件中有定义这个中间件

vendor/laravel/framework/src/Illuminate/Foundation/Http/Middleware/ConvertEmptyStringsToNull.php

<?php
 
namespace Illuminate\Foundation\Http\Middleware;
 
class ConvertEmptyStringsToNull extends TransformsRequest
{
    /**
     * Transform the given value.
     *
     * @param  string  $key
     * @param  mixed  $value
     * @return mixed
     */
    protected function transform($key, $value)
    {
        return is_string($value) && $value === '' ? null : $value;
    }
}

解决方法：

在 app/Http/Kernel.php 中注释掉 \Illuminate\Foundation\Http\Middleware\ConvertEmptyStringsToNull::class 即可

protected $middleware = [
        \App\Http\Middleware\TrustProxies::class,
        \App\Http\Middleware\CheckForMaintenanceMode::class,
        \Illuminate\Foundation\Http\Middleware\ValidatePostSize::class,
        \App\Http\Middleware\TrimStrings::class,
        //\Illuminate\Foundation\Http\Middleware\ConvertEmptyStringsToNull::class,
    ];