Merge pull request #210 from devplanete/patch-16

Update showCaptcha.php: code optimisation + check php gd extension

2-advanced/tools/showCaptcha.php

@@ -1,74 +1,74 @@
 <?php
 
 /**
- * a little bit dirty, but it works:
  * This file generates a captcha string, writes it into the $_SESSION['captcha']
- * and renders a fresh captcha graphic file to the browser. This is oldschool-non-PHP,
- * but it does the job.
+ * and renders a fresh captcha graphic file to the browser.
  * 
  * In the views you can use this by saying: 
  * <img src="tools/showCaptcha.php" />
  * 
  * Check if the typed captcha is correct by saying:
  * if ($_POST["captcha"] == $_SESSION['captcha']) { ... } else { ... }
- * 
  */
 
+// check if php gd extension is loaded
+if (!extension_loaded('gd')) {
+ die("It looks like GD is not installed");
+}
+
 session_start();
 
-// create set of usage characters
-$letters = array_merge( range('A', 'Z') , range(2, 9) );
-unset($letters[array_search('O', $letters)]);
-unset($letters[array_search('Q', $letters)]);
-unset($letters[array_search('I', $letters)]);
-unset($letters[array_search('5', $letters)]);
-unset($letters[array_search('S', $letters)]);
-shuffle($letters);
-$selected_letters = array_slice($letters, 0, 4);
-$secure_text = implode('', $selected_letters);
+// target captcha string length
+$iCaptchaLength = 4;
+
+// following letters are excluded from captcha: O, Q, I, 5, S
+$str_choice = 'ABCDEFGHJKLMNPRTUVWXYZ2346789';
+$str_captcha = '';
+// create target captcha with letters comming from $str_choice
+for ($i=0; $i < $iCaptchaLength; $i++) {
+ do {
+ $ipos = rand(0, strlen($str_choice) - 1);
+ // checks that each letter is used only once
+ } while (stripos($str_captcha, $str_choice[$ipos]) !== false);
 
-// write the 4 selected letters into a SESSION variable
-$_SESSION['captcha'] = $secure_text;
+ $str_captcha .= $str_choice[$ipos];
+}
 
-// get letters from SESSION, split them, create array of letters
-$letters = str_split($_SESSION['captcha']);
+// write the captcha into a SESSION variable
+$_SESSION['captcha'] = $str_captcha;
 
 // begin to create the image with PHP's GD tools
 $im = imagecreatetruecolor(150, 70);
-// TODO: error handling if creating images fails
-//or die("Cannot Initialize new GD image stream");
 
 $bg = imagecolorallocate($im, 255, 255, 255);
 imagefill($im, 0, 0, $bg);
 
 // create background with 1000 short lines
-/*
-for($i=0;$i<1000;$i++) {
+/*for($i=0;$i<1000;$i++) {
  $lines = imagecolorallocate($im, rand(200, 220), rand(200, 220), rand(200, 220));
  $start_x = rand(0,150);
  $start_y = rand(0,70);
  $end_x = $start_x + rand(0,5);
  $end_y = $start_y + rand(0,5);
  imageline($im, $start_x, $start_y, $end_x, $end_y, $lines);
-}
-*/
+}*/
 
 // create letters. for more info on how this works, please
 // @see php.net/manual/en/function.imagefttext.php
 // TODO: put the font path into the config
-$i = 0;
-foreach ($letters as $letter) {
- $text_color = imagecolorallocate($im, rand(0,100), rand(10,100), rand(0,100));
+for ($i=0; $i < $iCaptchaLength; $i++) {
+ $text_color = imagecolorallocate($im, rand(0, 100), rand(10, 100), rand(0, 100));
  // font-path relative to this file
- imagefttext($im, 35, rand(-10, 10), 20+($i*30) + rand(-5, +5), 35 + rand(10, 30), $text_color, 'fonts/times_new_yorker.ttf', $letter);
- $i++;
+ imagefttext($im, 35, rand(-10, 10), 20 + ($i * 30) + rand(-5, +5), 35 + rand(10, 30), $text_color, 'fonts/times_new_yorker.ttf', $str_captcha[$i]);
 }
 
 // send http-header to prevent image caching (so we always see a fresh captcha image)
 header('Content-type: image/png');
 header('Pragma: no-cache');
 header('Cache-Control: no-store, no-cache, proxy-revalidate');
 
-// send image to browser, destroy image from php "cache"
+// send image to browser and destroy image from php "cache"
 imagepng($im);
 imagedestroy($im);
+
+?>