- var_dump: documentation ( source)
- array_search: documentation ( source)
<?php
var_dump(['air_day' => ["Pazar","Pazartesi","Salı","Çarşamba","Perşembe","Cuma","Cumartesi"][array_search('Monday', ['Sunday', 'Monday', 'Tuesday', 'Wednesday', 'Thursday', 'Friday', 'Saturday'])],
]);