Yii2 Post to controller and get back data - yii2

Question

This is my code in view.
<?= $form->field($model, 'projectTitle')->dropDownList($fullprojectlist, [
'prompt'=>'-Choose a Course-',
'id' => 'projectList',
'type'=> 'POST',
'onchange'=>' var value = $("#projectList :selected").val();
//$("#draftproposalform-supervisor").val(value);'
$.post("'.Yii::$app->urlManager->createUrl(["/draftproposalform.php", "id" => value).'", function(data) {
//set value for text box
}
]);?>
<?= $form->field($model, 'supervisor')->textInput(['readonly'=> 'true']); ?>
I am trying to pass the selected value to the controller so that I can query the database to look for the relevant information. Then send back that information to the view to settext.
I know how to get data from the database. I just don't know how I can pass the selected value to controller and get back a value to settext while maintaining the selected value in view.
public function actionDraftproposalform() {
$model = new DraftProposalForm();
if($model->load(Yii::$app->request->post()) && $model->validate())
{
return $this->refresh();
}
else {
$query = new Query;
$query->select(['User.name', 'Project.title', 'Project.project_ID'])
->from('Project')
->innerJoin('Supervisor', '`Project`.`supervisor_ID` = `Supervisor`.`supervisor_ID`')
->innerJoin('User', '`Supervisor`.`user_ID` = `User`.`user_ID`')
->where(['Project.project_type_ID'=>1, 'Project.approval_ID'=>2]);
$projectlist = $query->all();
$fullprojectlist = ArrayHelper::map($projectlist, 'name', 'title', 'project_ID');
return $this->render('draftproposalform', [
'model'=>$model,
'fullprojectlist' => $fullprojectlist]);
}
}
Sorry if it's messy. Truthfully, I don't even know if passing the data back to here is the correct choice.
Edited Codes
View
<?php
$this->registerJs(' $("#projectList").change(function() {
var value = $("#projectList option:selected").val();
alert(value);
$.post(
"'.Yii::$app->urlManager->createUrl(["/draftproposalform.php"]).'",
{id:value},
function(data) {
alert("Test");
$("input[name=\'supervisor\']").val(data);
}); });');
?>
<?= $form->field($model, 'projectTitle')->dropDownList($projectlist, [
'prompt'=>'-Choose a Course-',
'id' => 'projectList',
'type'=> 'POST'
]);
?>
<?= $form->field($model, 'supervisor')->textInput(['readonly'=> 'true']); ?>
Controller
public function actionDraftproposalform() {
$model = new DraftProposalForm();
if(Yii::$app->request->isPost)
{
$id = Yii::$app->request->post("id");
$super = DbProject::findOne(["project_ID"=>$id]);
$supervisor = DbSupervisor::findOne(["supervisor_ID"=>$super->supervisor_ID]);
$user = DbUser::findOne(["user_ID"=>$supervisor->user_ID]);
//$super = DbSupervisor::findOne(["supervisor_ID"=>$id]);
echo $user->name;
exit;
}
else {
$projectlist = ArrayHelper::map(DbProject::find()->where(['project_type_ID' => 1, 'approval_ID' => 2])->asArray()->all(), 'project_ID', 'title');
return $this->render('draftproposalform', [
'model'=>$model,
'projectlist' => $projectlist]);
}
}

Answer 1

Can you test this.
//Controller
<?
public function actionDraftproposalform() {
$model = new DraftProposalForm();
if(Yii::$app->request->isPost)
{
$id=Yii::$app->request->post("id");
$super=Supervisor::findOne(["supervisor_ID"=>$id]);
if($super) echo $super->name;else echo "Not found";exit;
}
else {
$query = new Query;
$query->select(['User.name', 'Project.title', 'Project.project_ID'])
->from('Project')
->innerJoin('Supervisor', '`Project`.`supervisor_ID` = `Supervisor`.`supervisor_ID`')
->innerJoin('User', '`Supervisor`.`user_ID` = `User`.`user_ID`')
->where(['Project.project_type_ID'=>1, 'Project.approval_ID'=>2]);
$projectlist = $query->all();
$fullprojectlist = ArrayHelper::map($projectlist, 'name', 'title', 'project_ID');
return $this->render('draftproposalform', [
'model'=>$model,
'fullprojectlist' => $fullprojectlist]);
}
}
//view register js: put this in your view
<?
$this->registerJs(' $("#projectList").change(function(){
var value = $("#projectList option:selected").val();
$.post(
"'.Yii::$app->urlManager->createUrl(["/draftproposalform"]).'",
{ id:value },
function(data) {
$( "#draftproposalform-supervisor").val(data);
}); });');
?>