Somebody help with php and sms!

For a zillion days now I have been struggling with what I thought should have been a simple code.It is meant to accept a keyword from a mobile phone sent by sms to a page theoretically called smstry.php; and this page should if the keyword is correct send off a specific sms to another specific mobile phone.Like thus:


smstry.php
<?php
if($keyword)
{
//send off sms to clickatell gateway using ACCOUNT="pudding" and PASSWORD="ashton" with +2345678098 as destination;
}
else
{
//send off sms to Novelsoft gateway using different account and password combo with +11111222345 as destination;
}


How do I open a relationship with the appropriate gateway's cgi-bin in the absence of a submit button since these action are going to be carried out on a page that has no interface.
Thanks very mucho!

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