Basic usage example:
<code lang="PHP">
// Include the class
require 'class.swd_SMS.php';

// Create the object. (Parameters are optional if they're set in the class already)
$SMS = new swd_SMS('username', 'password');

// Send SMS. First parameter is the cell phone number with country code. (Without leading 00)
$SMS->send('34123456789', 'The message goes here');

// Let's send another just for fun
$SMS->send('34987654321', 'The message goes here');

// All sent messages are stored in an array.
echo '<pre>' . print_r($SMS->sent_messages, true) . '</pre>';


// Each sent message has a unique message ID, which is in the array above as well. With this we can see the message status any time. Like this:

$status = $SMS->fetch_msg_status('MT0052355965-1');

echo '<pre>' . print_r($status, true) . '</pre>';
</code>


And here's the class.
<code lang="PHP">
<?php

class swd_SMS
{

	/**
	*	=========================================================================
	*								SMS Class
	*	=========================================================================
	*
	*	@author:            Nicolas Oelgart
	*	@copyright:         Nicolas Oelgart
	*	@version:           Revision: 0.9
	*	@date:              22nd April 2007
	*	@last modified:     29th April 2007
	*	@license            GPL
	*
	*	@website:           www.nicoswd.com
	*	@email:             nico@nicoswd.com
	*
	*	@requirements:      PHP 5
	*
	*	=========================================================================
	*
	*	Copyright (C) 2007  Nicolas Oelgart
	*	
	*	This program is free software; you can redistribute it and/or modify it
	*	under the terms of the GNU General Public License as published by the
	*	Free Software Foundation; either version 2 of the License, or (at your
	*	option) any later version.
	*	
	*	This program is distributed in the hope that it will be useful, but
	*	WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
	*	or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
	*	for more details.
	*	
	*	You should have received a copy of the GNU General Public License along 
	*	with this program; if not, write to the Free Software Foundation, Inc., 
	*	51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
	*
	*	=========================================================================
	*/


	/**
	*	Your TM4B username. If you don't have one yet, register here for free:
	*	https://www.tm4b.com/register/
	*
	*	@type        string
	*/
	private $username         =  'username';

	/**
	*	Your TM4B login password.
	*
	*	@type        string
	*/
	private $password         =  'password';

	/**
	*	The SMS sender. Use your company name or whatever you want display
	*	to the recipient
	*
	*	@type       string
	*/
	private $from             =  'You';

	/**
	*	Message route. Both Global I and Global II messaging routes are
	*	identical with regards to reliability, delivery speed and support 
	*	for delivery states. More info here: http://www.tm4bhelp.com/kb/a-8.php#8
	*
	*	@type        string
	*/
	public $msg_route         =  'GD02';

	/**
	*	Minimum message length. Will set an error if the messags is shorter than
	*	this value.
	*
	*	@type        integer
	*/       
	public $msg_min_length    =  2;

	/**
	*	Maximum message length. Will set an error if the messags is larger than
	*	this value. If the message is larger than 160 chars, it will be split into
	*	2 or more messages.
	*
	*	@type        integer
	*/       
	public $msg_max_length    =  160;

	/**
	*	Minimum number length. Will set an error if the number is shorter than
	*	this value.
	*
	*	@type        integer
	*/       
	public $min_num_length    =  8;

	/**
	*	An array of errors that ocurred while any request.
	*
	*	@type        array
	*/       
	public $errors            =  array();

	/**
	*	An array with the details of the sent messages.
	*
	*	@type        array
	*/
	public $sent_messages     =  array();

	/**
	*	An array with all details of failed messages.
	*
	*	@type        array
	*/
	public $failed_messages   =  array();


	
	/**
	*	Class constructor. Takes 0 or 2 parameters. Parameter 1 being the username, 
	*	and parameter 2 being the password, for quick login.
	*
	*	@param       string        Login username
	*	@param       string        Login password
	*
	*	@return      none
	*/
	public function __construct()
	{
		if (func_num_args() == 2)
		{
			list($this->username, $this->password) = func_get_args();
		}
	}


	/**
	*	Sends the message out. The country code without the leading  00 must be
	*	specified in the number.
	*
	*	@param       string        Recipient phone number.
	*	@param       string        Message for recipient
	*	@param       string        "From" header.
	*	@param       string        Message route. Either GD01 or GD02
	*
	*	@return      boolean
	*/
	public function send($number, $message, $from = false, $route = false)
	{
		$number = preg_replace('/\D/', null, $number);

		if (strlen($number) < $this->min_num_length)
		{
			self::set_error("Invalid number: {$number}");
			return false;
		}
		
		// Convert message into a single line string.
		$message = preg_replace('/[\r\n\t]+/', ' ', trim(strval($message)));
		$message = preg_replace('/\s{2,}/', ' ', $message);
		$messagelength = strlen($message);

		if ($messagelength < $this->msg_min_length)
		{
			self::set_error('Message too short.');
			return false;
		}
		else if ($messagelength > $this->msg_max_length)
		{
			self::set_error('Message too long.');
			return false;
		}

		if ($from)
		{
			$this->from = $from;
		}
		if ($route AND in_array($route, array('GD01', 'GD02')))
		{
			$this->msg_route = $route;
		}

		$request = array(
			'version' => '2.0',
			'type'    => 'broadcast',
			'msg'     => $message,
			'to'      => $number,
			'from'    => $this->from,
			'route'   => $this->msg_route
		);

		$response = self::http_request($request);
		$request['delivertime'] = time();

		if (self::is_error($response))
		{
			array_push($this->failed_messages, $request);
			return false;
		}
		
		$request['messageid'] = $response;
		array_push($this->sent_messages, $request);
		return true;
	}

	
	/**
	*	Receives the message status and returns an array with the status and deliver time.
	*
	*	@param       string        Message ID
	*
	*	@return      array         Deliver status/Deliver time
	*/
	public function fetch_msg_status($messageid)
	{
		$request = array('type' => 'check_status');

		if (preg_match('/^MT[\d]{10}-\d$/', $messageid))
		{
			$request['id'] = $messageid;
		}
		else if (preg_match('/^[a-f0-9]{21}$/', $messageid))
		{
			$request['custom'] = $messageid;
		}
		else
		{
			self::set_error('Invalid Message ID.');
			return false;
		}

		$response = self::http_request($request);

		if (self::is_error($response))
		{
			return false;
		}

		list($status, $delivertime) = explode('|', $response);
		list($year, $month, $day, $hour, $minute) = str_split($delivertime, 2);
	
		return array(
			'delivered'   => ($status == 'DELIVRD'),
			'delivertime' => mktime($hour, $minute, 0, $month, $day, $year) // Don't we all prefer working with UNIX timestamps?
		);
	}


	/**
	*	Gets the current balance of your account.
	*
	*	@return      mixed        Balance on success, false on failure.
	*/
	public function fetch_balance()
	{
		$request = array(
			'version' => '2.0',
			'type'    => 'check_balance'
		);

		$response = self::http_request($request);

		return self::is_error($response) ? false : $response;
	}


	/**
	*	Checks if a specific destination is available on a message route
	*
	*	@param       string        Country code
	*	@param       string        Message route
	*
	*	@return      array         Availability, country, and credits needed to send SMS to this country
	*/
	public function check_destination($dest, $route = 'GD01')
	{
		$request = array(
			'type'  => 'check_destination',
			'dest'  => $dest,
			'route' => $route
		);

		$response = self::http_request($request);

		if (self::is_error($response))
		{
			return false;
		}

		@list($status, $country, $credits) = explode('|', $response);

		return array(
			'status'  => ($status == 'Yes'),
			'country' => $country,
			'credits' => $credits
		);
	}
	
	
	/**
	*	Sends the HTTP request to the server and receives the response.
	*	Either the cURL library needs to be installed, or allow_url_fopen
	*	needs to be enabled in php.ini
	*
	*	@param       array        request values
	*
	*	@return      string       Server response
	*/
	private function http_request($request = array())
	{
		// Should never exceed the time limit, but just in case.
		@set_time_limit(0);

		$request['username'] = $this->username;
		$request['password'] = $this->password;

		// Takes also care of the URL encoding.
		$request = http_build_query($request, '', '&');

		if (function_exists('curl_init') AND $ch = @curl_init('https://www.tm4b.com/client/api/http.php'))
		{
			curl_setopt($ch, CURLOPT_POST, true);
			curl_setopt($ch, CURLOPT_POSTFIELDS, $request);
			curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
			curl_setopt($ch, CURLOPT_SSL_VERIFYPEER, false);
		
			$response = curl_exec($ch);
			curl_close($ch);
		}
		else if (ini_get('allow_url_fopen'))
		{
			if (!$fp = @fsockopen('ssl://tm4b.com', 443))
			{
				self::set_error('Unable to connect to host. Try again later.');
				return false;
			}

			$header  = "POST /client/api/http.php HTTP/1.1\r\n";
			$header .= "Host: tm4b.com\r\n";
			$header .= "User-Agent: HTTP/1.1\r\n";
			$header .= "Content-Type: application/x-www-form-urlencoded\r\n";
			$header .= "Content-Length: " . strlen($request) . "\r\n";
			$header .= "Connection: close\r\n\r\n";
			$header .= "{$request}\r\n";
			
			fputs($fp, $header);
			$result = array();

			while(!feof($fp))
			{
				$result[] = fgets($fp);
			}

			fclose($fp);
			$response = $result[9];
		}
		else
		{
			trigger_error('Server does not support HTTP(S) requests.', E_USER_ERROR);
		}

		return trim($response);
	}


	/**
	*	Checks for errors in the API response and adds it to the array if there's one.
	*
	*	@param       string       API response
	*
	*	@return      boolean      True if error, false if not.
	*/
	private function is_error($string)
	{
		if (preg_match('/^error\(\d+\|([^\)]+)/', $string, $error))
		{
			self::set_error($error[1]);
			return true;
		}

		return false;
	}


	/**
	*	Sets the minumum and maximum message length
	*
	*	@param       integer        Minimum message length. Use false to keep default
	*	@param       integer        Maximum message length.
	*
	*	@return      none
	*/
	public function set_message_length($min, $max = false)
	{
		if ($min !== false)
		{
			$this->msg_min_length = intval($min);
		}
		if ($max !== false)
		{
			$this->msg_max_length = intval($max);
		}
	}
	
	
	/**
	*	Returns the number of sent messages.
	*
	*	@return       integer        Number of sent messages.
	*/
	public function nr_sentmessages()
	{
		return sizeof($this->sent_messages);
	}

	
	/**
	*	Adds an error string to the error array
	*
	*	@param       string       Error string
	*
	*	@return      none
	*/
	private function set_error($error)
	{
		$this->errors[] = $error;
	}

	/**
	*	=========================================================================
	*								SMS Class end
	*	=========================================================================
	*	Copyright (C) 2007 by Nicolas Oelgart.
	*/
	
}

?>
</code>