How to compose a regular expression in Yii2?

Question

Yii

There is an address:
sitename.ru/category/abc?letter=С
What regular expression is needed to be like this:
sitename.ru/category/abc/С
The last parameter changes, these are letters of the alphabet.
And also, there is another address:
sitename.ru/category/abc?letter=C&page=2
What regular expression is needed to be like this:
sitename.ru/category/abc/C/page/2

Answer 1

Use Named Parameters in URL Rules

'urlManager' => [
    'enablePrettyUrl' => true,
    'showScriptName' => false,
    'rules' => [
        // порядок следования правил важен для корректного формирования ссылок
        'category/abc/<letter:\w+>/page/<page:\d+>' => 'category/abc',
        'category/abc/<letter:\w+>' => 'category/abc',                
    ]
],