Send Bulk OTP SMS in PHP using SMS Gateway Center HTTP API
You need to be registered member with https://www.smsgatewaycenter.com/ and then you can use this script to send OTP SMS to your clients and peers.
This script is just an example to send sms and validate OTP using session. But you can use it with your database to get users and send out OTP SMS to registered members and have them validated.
About SMSGatewayCenter.com SMS Gateway Center is one of the leading Bulk SMS Gateway...
SMS plugin messenger with reliable SMS gateway connection.
...http://wordpress.org/extend/plugins/2-waysms-messenger/
http://downloads.wordpress.org/plugin/2-waysms-messenger.zip
Upload 2-waysms-messenger folder to the /wp-content/plugins/ directory
Activate the plugin through the 'Plugins' menu in WordPress
Go to 2-WaySMS Settings in adminpanel
To activate SMS sending enter your Token and Number and click Save
For SMS receiving, copy generated link from Receiver script field
Log in to your 2-WaySMS account http://www.2-waysms.com/my / My numbers / Settings
Set [Forward all Inbound Messages to the following URL] and paste copied link
Plugin ready for SMS sending and receiving