Phone voice call captcha powered by Twilio and TwiML (also forwards SMS)

twilio_captcha.php

<?php
/**
 * Call captcha to prevent spam calls
 * Uses Twilio TwiML syntax
 * @author abiusx
 * @version 1.1
 */
$name="John Doe"; // Put your name here
$number="+14342904141"; // Put your real phone number here

session_start(); // Store the challenge in session
header("Content-type: text/xml");
function logtext($text)
{
	@file_put_contents("call_log.txt",$text.PHP_EOL,FILE_APPEND);
}
$from=@$_POST['From']; // Caller number, e.g. +16175551212
$to=@$_POST['To']; // Our bot number, useful for handling multiple numbers with this code

if (@$_POST['Direction']!="inbound" and !isset($_POST['SmsSid'])) 
	return false; // Only process inbound calls

/// Available: $_POST['FromCity'],$_POST['FromState'],$_POST['FromZip'],$_POST['FromCountry']

$challenge_p1=rand(0,10);
$challenge_p2=rand(0,10);
$challenge_result=$challenge_p1+$challenge_p2;

$hints=["zero", "one", "two", "three", "four", "five", "six", "seven", "eight",
	"nine", "ten", "eleven", "twelve", "thirteen", "fourteen", "fifteen", "sixteen",
	"seventeen", "eighteen", "nineteen", "tewnty"];
$hint=$hints[$challenge_result];



// Response processing:
$response=null;
if (isset($_POST['Digits']))
{
	$response=$_POST['Digits'];
}
elseif (isset($_POST['SpeechResult']))
{
	$response=$_POST['SpeechResult'];
	// $_POST['Confidence'] is between 0.0 and 1.0
	if (!is_numeric($response))
	{
		if ( ($r=array_search($response, $hints)) !== false)
			$response=$r;
	}

}


echo '<?xml version="1.0" encoding="UTF-8"?>',PHP_EOL;
echo "<Response>",PHP_EOL;

if (isset($_POST['SmsSid']) or isset($_POST['Body'])) // SMS
{
	$body=$_POST['Body'];
	logtext("SMS Forwading from '{$from}' to '{$number}' saying '{$body}'");
	echo "<Message to='{$number}'>{$from}: {$body}</Message>\n";
}
else // Call
{

	if ($response!==null) // Response from caller
	{
		logtext("From: {$from}, To: {$to}, Response: {$response}");
		if (isset($_SESSION['result']) and $response==$_SESSION['result'])
		{
			echo "<Say voice='alice'>Thank you. Please wait while your call is connected.</Say>\n
				<Dial>{$number}</Dial>\n";
		}
		else
			echo "<Say voice='alice'>Invalid response. Good bye.</Say>\n";
	}
	else // Initial call
	{
		$_SESSION['result']=$challenge_result;
	?>
		<Gather input='dtmf speech' hints='<?=$hint;?>' numDigits='2' timeout='5'>
			<Say voice='alice'>You have called <?=$name;?>.
				If this is an unsolicited call, please hang up now.
				Otherwise, please respond to the following question for your call to be connected.
			</Say>
			<Pause />
			<Say voice='alice'>
				What is <?=$challenge_p1;?>+<?=$challenge_p2;?>?
			</Say>
			<Pause length='5' />
			<Say voice='alice'>
				I repeat, what is <?=$challenge_p1;?>+<?=$challenge_p2;?>?
			</Say>
		</Gather>
		<Say voice='alice'>You did not respond to the challenge. Good bye.</Say>
	<?php 
	}
}
echo "</Response>",PHP_EOL;