How to send messaaage to phone number from website using PHP...need urgent help.
Try searching first. Then when you get stuck with the code come back
Search for SMS gateway.
You'll discover there are many services offering SMS messaging, which you can connect to through their APIs. I bet most of these will be documented for PHP.
Alternatively you can connect directly to a network with either dedicated hardware or just a mobile phone.
Here are a some links that may help:
I found these with a simple DuckDuckGo (Google without the ads) search: Sending SMS messages from PHP
There were a bunch more that came back with in the results.