How to Integrate a SMS API in PHP?

How to Send SMS using PHP Program (full code sample included)?
How to send sms from localhost to mobile?
how to send message to mobile using php code?
how to send sms from website using php?
how to send otp sms using codeigniter?
how to send otp sms using php free?
how to send message in android programmatically?

All are the major questions for api developer. Please help me to integrate the same.