There exist number of SMS APIs in the market , but region to region there rates goes to very high price. A good API provider should have following specification.
There is an API provide called Twilio SMS API which is famous for there good rates and quick API respose.
Twilio SMS API is the best SMS API choice to embed for mobile verification and SMS alert. The response of Twilio SMS API is very quick and the rates are very affordable. Local and Toll-Free number rates started from $ 0.0075 per SMS. After 500K SMS they will provide 33 % discount also. Average Twilio SMS volume pricing First 500K Messages $ 0.0075 Next 4.5 Million Messages $ 0.0050 Next 20 Million Messages $ 0.0030
Here is an example of PHP code that how twilio SMS works.
Library Inclusion $client = new Twilio\Rest\Client($account_sid, $auth_token); $message = $client->messages->create( $phone, // Text this number array( 'from' => '+12365478912', // From a valid Twilio number 'body' => "Hello $Username, Your mobile confirmation code is $randomNumber Thanks Example Site " ) );