Why are some of my request parameters sent as `null` to my controller? - php

Question

I'm developing a LiveWire/Laravel project and in my product.blade.php, the category_id is sent as null to the store function. Apparently there is no problem in my input and my model and category_id is defineded in my component.
I used some artisan comands related to clearing the cache and config and even I created another component with different name but I met same bug
dd:
array:8 [▼
"title" => "تراکت"
"en_title" => "tracket"
"category_id" => null
"description" => "nothing"
"status" => 1
"img" => null
"price" => "48000"
"keywords" => "tracket"
]
Livewire Product Blade:
<div class="form-group">
<label class="form-label">دسته بندی محصول</label>
<select wire:model="category_id" id="select-countries" class="form-control custom-select">
#foreach($categories as $category)
<option value="{{$category->id}}">{{$category->title}}</option>
#if(count($category->childrenRecursive) >0)
#include('Admin.category.partials',['categories'=>$category->childrenRecursive,'level'=>1,'create'=>1])
#endif
#endforeach
</select>
</div>
Livewire Component :
<?php
class Index extends Component
{
public $title,$en_title,$category_id,$description,$status=1,$img=null,$price,$keywords;
public function store(){
$keywords=serialize(explode(",",$this->keywords));
Product::create([
'title'=>$this->title,
'en_title'=>$this->en_title,
'category_id'=>$this->category_id,
'description'=>$this->description,
'status'=>$this->status,
'price'=>$this->price,
'image'=>$this->img,
'keywords'=>$keywords,
]);
$this->reset(['title','en_title','category_id','description','price']);
session()->flash('add_product','محصول شما با موفقیت اضافه شد');
}
public function render()
{
$categories=Category::with('childrenRecursive')->where('parent_id',null)->get();
$products=Product::latest()->paginate(8);
return view('livewire.admin.product.index',compact('categories','products'))->extends('layouts.admin')->section('content');
}
}

Answer 1

Your syntax appears correct and I suspect you're sometimes seeing null because you're not setting an initial value for $category_id. Therefore, if you don't select an option from your select element and submit your form, the value of $category_id will be null.
You can perform some component initialization in the mount method where I suggest you set an initial value for your public properties:
public $categories, $products;
public $category_id;
public function mount()
{
$this->categories = Category::with('childrenRecursive')
->where('parent_id', null)
->get();
$this->products = Product::latest()->paginate(8);
$this->category_id = $this->categories->first()->id;
}
public function render()
{
return view(
'livewire.admin.product.index',
compact('categories','products')
)
->extends('layouts.admin')
->section('content');
}