PHP custom codes substr message

PHP custom codes substr message

I have 10 variables with some data (confirmation keys, url, different
message etc).:
$confirmation_key = "http://www.example.com/?key=127e9kK";
$web_url = "www.example.com";
$welcome_message = "Hello, welcome to our program!";
I want make replace $show_now contents with codes, I will write one example.
$show_now = "Hi, thank you for registration, please check url:
{confirmation_key}. Best regards {web_url}";
must be replaced to:
$show_now = "Hi, thank you for registration, please check url:
http://www.example.com/?key=127e9kK. Best regards www.example.com";