How to send text messages to site users

I have a site that I would like to send all of the users (20-100) text messages about 2 or 3 times a year. What are my options? and how do I implement this into a php/mysql based site?

Any and all suggestions are welcome. Feel free to let me开发者_JAVA技巧 know if I need to provide more information for clarity.

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You might try something like this.

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You have to buy an SMS gateway API from the vendor and implement with that www.SMSCountry.com is a good option