php - foreign key not define in migration file in Laravel 5.2 -

i have 2 migration files in laravel app projects , task. project id column foreign key task table project_id. need save project id project_id in task table. did not configure foreign key ralationship in task migration file task migration file

public function up()     {          schema::create('tasks', function(blueprint $table)         {             $table->increments('id')->unsigned();             $table->longtext('task_name');             $table->text('body');             $table->string('assign');             $table->string('priority');             $table->date('duedate');             $table->integer('project_id')->unsigned();             $table->timestamps();  });      } 

this taskcontroller

public function postnewtask(request $request, project $project) {     $task = new task;     $task->task_name   = $request->input('name');     $task->body = $request->input('body');     $task->assign = $request->input('status');     $task->priority = $request->input('status');      $task->duedate  = date("y-m-d", strtotime($request->input("date")));      $task->project_id = $project->id;     // set project_id on task , save     $project->tasks()->save($task);  } 

task model

class task extends model {      protected $fillable = ['task_name', 'body', 'assign','priority','duedate','project_id'];  public function scopeproject($query, $id)     {         return $query->where('project_id', $id);     }        public function project()      {          return $this->belongsto('app\project');      } 

project model

class project extends model {     protected $fillable = ['project_name','project_notes','project_status','color','group'];     //      public function tasks(){          return $this->hasmany('app\task'); 

my form action

<form  method="post" action="{{ route('projects.tasks.create', $project->id) }}"> 

and routes

route::post('projects/{projects}/tasks', [     'uses' => '\app\http\controllers\taskscontroller@postnewtask',     'as' => 'projects.tasks.create' ]); 

but when going save form data has occurred following error message

sqlstate[23000]: integrity constraint violation: 1048 column 'project_id' cannot null 

how can solved problem. migration file foreign key not define problem?

finally got results taskcontroller

  public function postnewtask(request $request,$id, project $project)     {          $task = new task;         $task->task_name   = $request->input('name');         $task->body = $request->input('body');         $task->assign = $request->input('status');         $task->priority = $request->input('status');         $task->duedate  = date("y-m-d", strtotime($request->input("date")));         $task->project_id = $id;         $task->save(); }