Yii2, optional parameter in the rounte - yii

Question

During the development, I have faced to the one issue with urlManager.
I have SiteController with "category" action.
public function actionCategory($id = null, $city = null, $location = null)
{
echo $id;
echo $city;
echo $location;
}
All possible combination that can be used with this action:
id, city, location = null
id, city = null, location
id, city = null, location = null
id = null, city = null, location = null
id = null, city = null, location
I do not know how to write the rules in the UrlManager, after that I will get the following values in the variables after press the links:
<h4><?= Html::a('ID City', ['/site/category', 'id' => 'barbershop', 'city' => 'Praha'], ['class' => 'btn btn-primary']) ?></h4>
The return value from "category" action:
id = 'barbershop'
city = 'Praha'
location = ''
<h4><?= Html::a('ID Location', ['/site/category', 'id' => 'barbershop', 'location' => '23,65'], ['class' => 'btn btn-primary']) ?></h4>
The return value from "category" action:
id = 'barbershop'
city = ''
location = '23,65'
<h4><?= Html::a('ID', ['/site/category', 'id' => 'barbershop'], ['class' => 'btn btn-primary']) ?></h4>
The return value from "category" action:
id = 'barbershop'
city = ''
location = ''
<h4><?= Html::a('City', ['/site/category', 'city' => 'Praha'], ['class' => 'btn btn-primary']) ?></h4>
The return value from "category" action:
id = ''
city = 'Praha'
location = ''
<h4><?= Html::a('Location', ['/site/category', 'location' => '14,23'], ['class' => 'btn btn-primary']) ?></h4>
The return value from "category" action:
id = ''
city = ''
location = '14,23'
Would you like you help me with this issue?

Answer 1

As per your requirements you need to set rules only for Controller and action name. All other fields are passed through $_GET. and you can fetch them using Yii::$app->getRequest()->getQueryParam('param') method.
For you url you can use normal rules for pretty url like
'urlManager' => [
'enablePrettyUrl' => true,
'showScriptName' => false,
'rules' => [
'<controller:\w+>/<id:\d+>' => '<controller>/view',
'<controller:\w+>/<action:\w+>/<id:\d+>' => '<controller>/<action>',
'<controller:\w+>/<action:\w+>' => '<controller>/<action>',
],
],