get value of selected dropdown option in yii2 controller

I'm trying to get value of selected dropdown menu from signup form. i need to store that value in db. dropdown code is.

<?= $form->field($model, 'sex')->dropDownList(['1' => 'Male', '2' => 'Female'],['prompt'=>'Select Gender...'] )?>

I have tried with property 'sex[]' here. but it didn't help.

i have tried in controller with post request.

 $post=Yii::$app->request->post();
    $chosen = Yii::$app->request->post('sex', '');

    print_r($chosen);
    print_r($post->sex);

    echo "1:".$this->sex;
    echo "<br>";
    echo "2:".$this->sex;
    echo "<br>";
    echo "3:".$this->sex[0];
    echo "<br>";
    echo "4:".$this->sex[1];
    echo "<br>";

but non of these printed the vlaue in post submitted. it contains the value for sex. here is the print_r($post) result [sex]=>1 but if is use'sex[]'in dropdown it shows something like [sex]=>array( [0]=>1)

if you want to select more than one, make sure that you create it as array in form Property sex[]

like this

<?= $form->field($model, 'sex[]')->dropDownList(['1' => 'Male', '2' => 'Female'],['prompt'=>'Select Gender...'] )?>

then load it to your model

$model->load(Yii::$app->request->post()) 

it would be

$model->sex (that is an array).

if you want to select just one option

you have to had something like this

<?= $form->field($model, 'sex')->.... ?>

and your answer will be $model->sex (that is 1 or 2)