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Simple image CAPTCHA

/ Published in: PHP
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In img tag set src=\"captcha.php\"

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  1. <?php
  2.  
  3. function create_captcha($char_count = 6)
  4. {
  5. 	$possible = '23456789bcdfghjkmnpqrstvwxyz';
  6. 	$security_code = '';
  7. 	$i = 0;
  8. 	while ($i < $char_count) {
  9. 		$security_code .= substr($possible, mt_rand(0, strlen($possible)-1), 1);
  10. 		$i++;
  11. 	}
  12.  
  13.     //Set the session to store the security code
  14.     $_SESSION["captcha_code"] = $security_code;
  15.  
  16.     $width = 100;
  17.     $height = 25;
  18.  
  19.     //Create the image resource
  20.     $image = ImageCreate($width, $height);
  21.  
  22.     //We are making three colors, white, black and gray
  23.     $white = ImageColorAllocate($image, 255, 255, 255);
  24.     $black = ImageColorAllocate($image, 0, 0, 0);
  25.     $grey = ImageColorAllocate($image, 204, 204, 204);
  26.  
  27.     //Make the background black
  28.     ImageFill($image, 0, 0, $black);
  29.  
  30.     //Add randomly generated string in white to the image
  31.     ImageString($image, 5, 30, 3, $security_code, $white);
  32.  
  33.     //Throw in some lines to make it a little bit harder for any bots to break
  34.     ImageRectangle($image,0,0,$width-1,$height-1,$grey);
  35.     imageline($image, 0, 5, $width, 5, $grey);
  36.     imageline($image, $width/4, 0, $width/2, $height, $grey);
  37.     imageline($image, 0, 18, $width, 18, $grey);
  38.     imageline($image, 46, 0, 86, $height, $grey);
  39.  
  40.     header("Content-Type: image/jpeg");
  41.  
  42.     //Output the newly created image in jpeg format
  43.     ImageJpeg($image);
  44.  
  45.     //Free up resources
  46.     ImageDestroy($image);
  47. }
  48.  
  49. create_captcha();
  50.  
  51. ?>

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