How to add verify mobile number through otp feature through html ,css,js,php or any other languages

Question

How to add verify mobile number through otp so automatically otp sent to that number within seconds.

Answer 1

without external services it could be tricky as you need to know the sms gateway details of the network operator your user is subscribed to.
there are easier solutions but they usually come at a cost.
https://code.tutsplus.com/tutorials/how-to-send-text-messages-with-php--net-17693