<?PHP session_start();





function generateCode($characters) 


{


		/* list all possible characters, similar looking characters and vowels have been removed */


		$possible = '123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ';


		$code = '';


		$i = 0;


		while ($i < $characters) { 


			$code .= substr($possible, mt_rand(0, strlen($possible)-1), 1);


			$i++;


		}


		return $code;


}





		$width =  '250';


		$height = '90';


		$characters = '5';


		


		$code = generateCode($characters);


		/* font size will be 75% of the image height */


		$font_size = 40;//$height * 0.45; //10;//


		$image = @imagecreate($width, $height) or die('Cannot initialize new GD image stream');


		/* set the colours */


		$background_color = imagecolorallocate($image, 0, 0, 0);


		$text_color = imagecolorallocate($image, 255, 255, 255);


		$noise_color = imagecolorallocate($image, 0, 0, 0);


		/* generate random dots in background */


		for( $i=0; $i<($width*$height)/5; $i++ ) {


			imagefilledellipse($image, mt_rand(0,$width), mt_rand(0,$height), 1, 1, $noise_color);


		}


		/* generate random lines in background */


		for( $i=0; $i<($width*$height)/300; $i++ ) {


			imageline($image, mt_rand(0,$width), mt_rand(0,$height), mt_rand(0,$width), mt_rand(0,$height), $noise_color);


		}


		/* create textbox and add text */


		$textbox = imagettfbbox($font_size, 0,  "images/arial.ttf", $code) or die('Error in imagettfbbox function');


		$x = ($width - $textbox[4])/2;


		$y = ($height - $textbox[5])/2;


		imagettftext($image, $font_size, 0, $x, $y, $text_color,  "images/arial.ttf" , $code) or die('Error in imagettftext function');


		/* output captcha image to browser */


		header('Content-Type: image/jpeg');


		header('Cache-Control: no-cache, must-revalidate');


		imagejpeg($image);


		imagedestroy($image);


		$_SESSION['security_code'] = $code;		


	





	





?>