Searches for a hashtag in a set list of users' timelines, and SMSes the contents to a number using Twilio API. Uses basic MySQL store for preventing duplicate SMSes. Uses fancy tweet entities for hashtag detection.

Twitter Hashtag to SMS.php

<?php
$link = mysql_connect('localhost', 'username', 'password');
mysql_select_db('database_name');
$users = array('user_a', 'user_b', 'user_c',  'user_d'); //twitter handles, must be public timelines
$post_array = array('To'=>('1XXX5551234'), 'From'=>('1XXX5551234')); //FROM must be a Twilio-purchased #
$followed_hashtag = 'blahblah'; //will follow #blahblah hashtag in the users tweets
foreach($users as $user) 
{
$url = "http://api.twitter.com/1/statuses/user_timeline.json?screen_name=" . $user . '&include_entities=true&trim_user=true';
$user_stream = json_decode(file_get_contents($url), true);
	foreach($user_stream as $tweet)
	{ 
		$rows = mysql_num_rows(mysql_query('SELECT * FROM tweet_to_sms_archive WHERE tweet_id="'.$tweet['id_str'].'"' ));
		if(!$rows && $tweet['entities']['hashtags'])
		{
			foreach($tweet['entities']['hashtags'] as $hashtag_array)
			{
				if(strtolower($hashtag_array['text'])==$followed_hashtag)
				{
					$this_sms = $post_array;
					echo $tweet['text'];
					$this_sms['Body'] = utf8_encode('' . $user . ': ' . $tweet['text']);
				if(send_sms($this_sms))
				{
					$sql = 'INSERT INTO tweet_to_sms_archive (tweet_id,body) VALUES ('. $tweet['id_str'] . ',"' .mysql_real_escape_string(json_encode($tweet)) .'")';
				}
				}
			}
		}
	} 
}

function send_sms($post)
{
$encoded = ""; 
$user_name = ''; //from twilio
$pw = ''; //from twilio
foreach($post AS $key=>$value)
    $encoded .= "$key=".urlencode($value)."&";
	$encoded = substr($encoded, 0, -1);
	$twilio_url = "https://api.twilio.com/2010-04-01/Accounts/$user_name/SMS/Messages";
	$ch = curl_init();
	curl_setopt($ch, CURLOPT_URL, $twilio_url);
	curl_setopt($ch, CURLOPT_POST, true);
	curl_setopt($ch, CURLOPT_SSL_VERIFYPEER, false);
	curl_setopt($ch,CURLOPT_USERPWD,"$user_name:$pw"); 
	curl_setopt($ch, CURLOPT_HTTPHEADER, array("Content-type: application/x-www-form-urlencoded;charset=UTF-8"));
	curl_setopt($ch, CURLOPT_POSTFIELDS, $encoded);
	curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
	$result = curl_exec($ch);
	curl_close($ch);
	return $result;
}
?>