php部分逻辑

public function article_list(){
 //echo 'zoule';exit; 测试表单是否走进方法中 大家随意写
 $shownum = 1;
 if(array_key_exists('class',$_GET)||array_key_exists('keywords',$_GET)){
  //echo '111';
  if($_GET['class']){
  //Article模型 leftJoin表连接 查询根据俩个表里的这些字段来执行
    $postdata = Article::leftJoin('category', function($join) {
     $join->on('article.class_id', '=', 'category.id');
    })->select(['article.id','category.class_name','article.status','article.title_editing','article.update_time'])->where('article.class_id','=',$_GET['class'])->orderBy('release_time','desc')->paginate($shownum);
  }elseif($_GET['keywords']){
    $postdata = Article::leftJoin('category', function($join) {
     $join->on('article.class_id', '=', 'category.id');
    })->select(['article.id','category.class_name','article.status','article.title_editing','article.update_time'])->where('article.title_editing','=',$_GET['keywords'])->orderBy('release_time','desc')->paginate($shownum);
   
  }else{
    $postdata = Article::leftJoin('category', function($join) {
     $join->on('article.class_id', '=', 'category.id');
    })->select(['article.id','category.class_name','article.status','article.title_editing','article.update_time'])->orderBy('release_time','desc')->paginate($shownum);
  }
 }else{
  //echo '2222';
  $postdata = Article::leftJoin('category', function($join) {
    $join->on('article.class_id', '=', 'category.id');
  })->select(['article.id','category.class_name','article.status','article.title_editing','article.update_time'])->orderBy('release_time','desc')->paginate($shownum);
 }
 //分类id不是父id
 $category = DB::table('category')->where('parent_id','!=','0')->get();
 //渲染页面 传递 参数
 return view('backend.article_list',['postdata'=>$postdata,'shownum'=>$shownum,'category'=>$category]);
}