//start session which will be used to store generated numbers of validation in the form 

session_start(); 

//generate random number between 10,000 and 99999 

$number =mt_rand(10000, 99999); 

//store generate random number to a session 

$_SESSION['answer']=$number; 

//create image 50 x 50 pixels 

$imagecreate = imagecreate(50, 50); 

// white background and blue text 

$background = imagecolorallocate($imagecreate, 255, 255, 255); 

$textcolor = imagecolorallocate($imagecreate, 0, 0, 255); 

// write the string at the top left 

imagestring($imagecreate, 5, 5, 10, $number, $textcolor); 

// output the image 

header("Content-type: image/png"); 

$image= imagepng($imagecreate);

$username = "username"; 

$password = "password"; 

$hostname = "localhost"; 

$database = "captcha"; 

$dbhandle = mysql_connect($hostname, $username, $password) or die("Unable to connect to MySQL"); 

$selected = mysql_select_db($database,$dbhandle) or die("Could not select $database"); 

echo 'Enter captcha (Case sensitive for security measure) <br/>'; 

echo '<input type="text" name="cvd" size="50">'; 

//generate captcha 

$random= rand(1,12); 

$random = mysql_real_escape_string(stripslashes($random)); 

$result2 = mysql_query("SELECT `imagepath` FROM `captcha` WHERE `number`='$random'") or die(mysql_error()); 

$row = mysql_fetch_array($result2) or die("Invalid query: " . mysql_error()); 

$captcha = $row['imagepath']; 

echo '<img src="'.$captcha.'"/>'; 

$random = mysql_real_escape_string(stripslashes($random)); 

//extract answer of captcha 

$result3 = mysql_query("SELECT `answer` FROM `captcha` WHERE `number`='$random'") or die(mysql_error()); 

$row = mysql_fetch_array($result3) or die("Invalid query: " . mysql_error()); 

$answer = $row['answer']; 

//store answer to a session variable 

$_SESSION['captchaanswer']=$answer;