BotDetect CAPTCHA Options: Application Config Settings Code Example

The PHP Captcha options: Application config settings code example shows how to configure Captcha challenges by overriding Captcha library defaults in application configuration files.

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BotDetect allows user-defined customization of many Captcha options through a special CaptchaConfig.php file, which should be placed in the same folder as the botdetect.php include used by your PHP forms.

Captcha settings from this configuration file will apply to all Captcha challenges shown on forms including that particular copy of botdetect.php, and will act as defaults with which all Captcha objects will be created. This makes configuration file settings the simplest and most convenient way of Captcha customization for most use cases.

The CaptchaConfig.php file used in this code example contains detailed descriptions and explanations of the many customizable Captcha options exposed by the BotDetect PHP Captcha configuration API.

Downloaded Location

The PHP Captcha options: Application config settings code example is included in the examples/captcha-application-config-settings-example folder of the download package.

Download the BotDetect PHP CAPTCHA Library and run this example

index.php

<?php session_start(); ?>
<?php require("custom-captcha-request-handler.php"); ?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN"
 "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">

<html xmlns="http://www.w3.org/1999/xhtml" >
<head>
  <title>BotDetect PHP CAPTCHA Options:
   Application Config Settings Code Example</title>
  <meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />
  <link type="text/css" rel="Stylesheet"
    href="<?php echo CaptchaUrls::LayoutStylesheetUrl() ?>" />
  <link type="text/css" rel="Stylesheet" href="stylesheet.css" />
  <script type="text/javascript"
    src="<?php echo CaptchaUrls::ScriptIncludeUrl() ?>"></script>
</head>
<body>
  <form method="post" action="" class="column" id="form1">

    <h1>BotDetect PHP CAPTCHA Options: <br />
       Application Config Settings Code Example</h1>

    <fieldset>
      <legend>PHP CAPTCHA validation</legend>
      <label for="CaptchaCode">Retype the characters from the picture:</label>

      <?php // Adding BotDetect Captcha to the page
        $AppConfigCustomizedCaptcha = new Captcha("AppConfigCustomizedCaptcha");
        $AppConfigCustomizedCaptcha->UserInputID = "CaptchaCode";
        echo $AppConfigCustomizedCaptcha->Html();
      ?>

      <div class="validationDiv">
        <input name="CaptchaCode" type="text" id="CaptchaCode" />
        <input type="submit" name="ValidateCaptchaButton" id="ValidateCaptchaButton"
         value="Validate" />
        <?php // when the form is submitted
          if ($_POST) {
            // validate the Captcha to check we're not dealing with a bot
            $isHuman = $AppConfigCustomizedCaptcha->Validate();

            if (!$isHuman) {
              // Captcha validation failed, show error message
              echo "<span class=\"incorrect\">Incorrect code</span>";
            } else {
              // Captcha validation passed, perform protected action
              echo "<span class=\"correct\">Correct code</span>";
            }
          }
        ?>
      </div>
    </fieldset>
  </form>
</body>
</html>

In the form source, we don't follow the non-standard procedure for adding Captcha protection to a PHP form, i.e we're using the custom-captcha-request-handler.php file instead of botdetct.php in default to process Captcha challenge Http requests.

CaptchaConfig.php

<?php

// BotDetect PHP Captcha configuration options


// Captcha codes
// ---------------------------------------------------------------------------

// Number of characters in randomly generated Captcha codes (answers to Captcha 
// challenges).
// The default value is random (4-6 characters).
// Valid user Captcha code length setting values are integers larger than 0 and 
// smaller than 16.
// It is recommended to always randomize Captcha code length since it 
// significantly increases Captcha security vs. automated analysis.
$BotDetect->CodeLength = CaptchaRandomization::GetRandomCodeLength(3, 5);

// Character types used to generate random Captcha codes. 
// The default value is Alphanumeric.
// Valid user Captcha code style setting values are members of the BotDetect
// CodeStyle enumeration (Alpha, Numeric, or Alphanumeric).
// Since entropy of the Captcha challenge depends on character set size to 
// the power of Captcha code length, alpha codes should be slightly longer 
// than alphanumeric ones (while numeric Captcha codes should be significantly
// longer) to achieve an appropriate level of Captcha security. 
$BotDetect->CodeStyle = CodeStyle::Alpha;

// Strings that should never occur in randomly generated Captcha codes. Can be 
// both single characters (allows Captcha character set customization) and 
// sequences of two or more characters (useful for swear words filtering, avoiding
// particular hard-to-read sequences etc.).
// The default value is empty (Captcha code filtering is optional).
// Valid user disallowed Captcha code substring setting values are lists of 
// arbitrary strings, in CSV format. Whitespace is ignored, and disallowed 
// substrings are not case-sensitive (because Captcha codes are case-insensitive 
// as well). 
// The character set used for Captcha code generation is automatically chosen 
// based on Captcha locale. Since each character needs to have its pronunciation 
// recorded and available to BotDetect code, expanding that default character set 
// to include new characters is not supported (it would break Captcha sound 
// functionality). However, if a particular character is found hard to read, 
// it can easily be excluded from randomly generated Captcha codes. Furthermore, 
// offensive or otherwise undesirable words and character sequences can be banned.
// Since Captcha codes are generally short, it doesn't make sense to use an 
// actual dictionary of words, but simple short sequences that cover multiple 
// disallowed values. E.g. to prevent the random generator from using both 'man',
// 'manners' and 'mannequin' in Captcha codes, it's enough to ban the 'man' 
// sequence.
$BotDetect->DisallowedCodeSubstrings = 'd,e,f,g,h,i,j,k,l,m,n,o,p,q,r,s,t,u,v,w,x,y,z,aa,bb,cc,abc,bca,cab';

// The time period after random Captcha code generation during which Captcha 
// challenges based on it can be solved: when it expires, even correct inputs 
// will be considered as invalid submissions.
// The default value is 1200 seconds (20 minutes).
// Valid user Captcha code timeout setting values are integers larger than 30 
// and smaller than 7200 (i.e. between half a minute and 2 hours). 
// Reducing the Captcha code timeout is an optional security improvement that
// narrows the window of opportunity for attacks based on reusing the Captcha 
// challenge on another site controlled by the attacker, proxying it to human 
// solvers, or similar attempts to bypass the Captcha protection. However, to 
// meet usability criteria, users filling out the form should always be given 
// reasonably enough time to solve the Captcha challenge. Since Captcha codes 
// are stored in Session state by default, please note that if the configured 
// code timeout is longer than the active Session timeout, Captcha validation 
// will still fail if the user Session expires due to inactivity.
$BotDetect->CodeTimeout = 600;

// Application configuration switch to use if you want to run automated tests 
// that need to be able to submit a Captcha-protected form in QA environments.
// The default value is false.
// Valid user Captcha test mode setting values are booleans.
// When test mode is enabled, it makes the Captcha challenge trivially solvable 
// (always using "TEST" as the solution instead of a random sequence of 
// characters). Be careful NEVER to enable this on production websites by 
// mistake, since it will allow bots to trivially bypass the Captcha, but will 
// still provide an obstacle for human users. Because of the serious security 
// implications if the Captcha test mode setting is misapplied, it can only be 
// enabled globally for the whole application (individual forms and Captcha 
// object instances can't change it), and will display a warning in generated 
// Captcha container markup.
$BotDetect->TestModeEnabled = false;


// Captcha images
// ---------------------------------------------------------------------------

// The BotDetect drawing algorithm used to render Captcha codes in image Captcha 
// challenges.
// The default value is random (an image style is chosen from all available 
// values for each Captcha image generated).
// Valid user Captcha image style setting values are members of the BotDetect 
// ImageStyle enumeration. Please note that some image styles are restricted to 
// paid versions of BotDetect, and will be ignored in free version 
// implementations.
// It's best to randomize the Captcha image style, since randomly choosing a 
// style for each Captcha image generated provides the highest level of Captcha 
// security against automated OCR analysis.
$imageStyles = array(
  ImageStyle::Chipped, 
  ImageStyle::Fingerprints, 
  ImageStyle::Graffiti, 
  ImageStyle::Bullets
);
$BotDetect->ImageStyle = CaptchaRandomization::GetRandomImageStyle($imageStyles);

// Size of Captcha image challenges generated.
// The default value is 250 x 50 pixels.
// Valid user Captcha image size setting values are integers: widths can be 
// between 20 and 500 pixels and heights between 20 and 200 pixels.
// To keep Captcha images reasonably readable, their width:height ratio 
// should be approximately the same as the average Captcha code length.ls
$BotDetect->ImageWidth = 200;
$BotDetect->ImageHeight = 50;

// Image format in which Captcha images will be generated and sent to the client.
// The default value is Jpeg.
// Valid user Captcha image format setting values are members of the BotDetect 
// ImageFormat enumeration (Jpeg, Png, Gif).
// Please note that some Captcha image styles will result in low-quality 
// (pixelated) images when the image format is set to Gif, due to randomized 
// color schemes and use of color gradients. When switching image formats, 
// please take care to check the impact on Captcha image readability.
$BotDetect->ImageFormat = ImageFormat::Png;

// BotDetect allows Captcha image color scheme customization though two color 
// points: a custom dark color and a custom light color. 
// The default values are empty (Captcha color customization is optional).
// Valid user Captcha custom dark / light color setting values are Html colors, 
// so you can use both predefined color names and custom color hex values.
// Since many Captcha drawing styles randomize the actual color used, the 
// user-defined values are used as randomization starting points instead of 
// absolute values. Furthermore, since some drawing styles use light text on 
// a dark background, while other draw dark text on a light background, text 
// and background colors are not set directly, but are referred to as simply 
// the "dark" and the "light" color. This allows you to randomize the image 
// drawing style, for example, and still keep a consistent color scheme 
// adjusted to your website design.
$BotDetect->CustomDarkColor = '#483d8b';
$BotDetect->CustomLightColor = '#87cefa';

// Application configuration setting that allows centralized temporary 
// disabling of individual BotDetect image styles if there is ever an urgent 
// issue that requires it. 
// The default value is empty (image style disabling is an optional feature 
// meant for short-term use during exceptional situations).
// Valid user disabled image styles setting values are CSV strings of ImageStyle 
// names (case-insensitive, separator whitespace is ignored).
// BotDetect image styles used on user forms can be configured in different ways 
// (a single static value, a randomized value, a dynamic value that adapts to 
// visitor behavior) and can apply to all Captcha instances in an application 
// or be specific to a particular Captcha challenge placed on a single form. If 
// an urgent issue is ever discovered in a BotDetect image style implementation 
// (e.g. a bug causing it to throw errors in certain circumstances, or a 
// weakness allowing some forms of automated analysis to bypass it, or a 
// memory leak etc.), users should be able to deactivate the problematic 
// ImageStyle while they're waiting for issue resolution. This BotDetect 
// setting acts as a centralized application configuration switch which allows 
// such image style deactivation, without requiring users to examine and 
// possibly modify all of their source code that might be affected. It also 
// makes it much easier to revert the change later when the issue gets fixed.
$BotDetect->DisabledImageStyles = 'Chipped,Lego,Wave';


// Captcha sounds
// ---------------------------------------------------------------------------

// Is Captcha sound enabled.
// The default value is true.
// Valid user Captcha sound enabled setting values are booleans.
// Captcha sound can be disabled entirely (for example if you are using the 
// free version of BotDetect, which only supports demo sound that is not 
// actually accessible to human visitors) by setting this property to false. 
$BotDetect->SoundEnabled = true;

// The BotDetect audio generation algorithm used to pronounce Captcha codes in 
// sound Captcha challenges.
// The default value is random (a sound style is chosen from all available 
// values for each Captcha sound generated).
// Valid user Captcha sound style setting values are members of the BotDetect 
// SoundStyle enumeration. Please note that some sound styles are restricted 
// to paid versions of BotDetect, and will be ignored in free version 
// implementations.
// It's best to randomize the Captcha sound style, since randomly choosing a 
// style for each Captcha sound generated provides the highest level of Captcha 
// security against automated audio analysis and voice recognition.
$soundStyles = array(
  SoundStyle::Dispatch, 
  SoundStyle::RedAlert, 
  SoundStyle::Synth
);
$BotDetect->SoundStyle = CaptchaRandomization::GetRandomSoundStyle($soundStyles);

// Audio format in which Captcha sounds will be generated and sent to the client.
// The default value is WavPcm16bit8kHzMono.
// Valid user Captcha sound format setting values are members of the BotDetect 
// SoundFormat enumeration (WavPcm16bit8kHzMono, WavPcm8bit8kHzMono).
// Using 8 bit sound instead of default 16 bits per example lowers the WAV file 
// download size, but reduces sound quality.
$BotDetect->SoundFormat = SoundFormat::WavPcm16bit8kHzMono;

// How will multiple consecutive requests for audio Captcha with the same 
// Captcha code ("sound regeneration") be handled by BotDetect - a tradeoff 
// of security, usability, and storage requirements.
// The default value is Limited.
// Valid user Captcha sound regeneration mode setting values are members of the 
// BotDetect SoundRegenerationMode enumeration (None, Limited, Unlimited).
// BotDetect defaults to limited sound regeneration as the most reasonable 
// overall trade-off. At user discretion, higher security and usability can be 
// achieved by disabling sound regeneration at the cost of significant amounts 
// of server-side storage space. Unlimited sound regeneration is not recommended 
// due to low security, but is left as an option for backwards-compatibility.
$BotDetect->SoundRegenerationMode = SoundRegenerationMode::None;

// Application configuration setting that controls whether BotDetect disables 
// (greys-out and prevents clicks on) the Captcha sound icon and displays a 
// warning tooltip when the sound package file containing character 
// pronunciations for the currently set Captcha locale can not be found.
// The default value is true (display a warning when the required .bdsp file 
// cannot be found).
// Valid user warn about missing sound packages setting values are booleans.
// Warnings about missing sound packages help during development and deployment, 
// so you don't mistakenly forget to download and copy the needed files. 
// However, this warning is not meant for (and should never be seen by) site 
// visitors. So if you didn't copy a particular sound package because you 
// intentionally don't want to support audio Captcha sounds in that language, 
// you can disable the warning (and the sound icon for such locales).
$BotDetect->WarnAboutMissingSoundPackages = false;

// Application configuration setting that allows centralized temporary 
// disabling of individual BotDetect sound styles if there is ever an urgent 
// issue that requires it. 
// The default value is empty (sound style disabling is an optional feature 
// meant for short-term use during exceptional situations).
// Valid user disabled sound styles setting values are CSV strings of SoundStyle 
// names (case-insensitive, separator whitespace is ignored).
// BotDetect sound styles used on user forms can be configured in different ways 
// (a single static value, a randomized value, a dynamic value that adapts to 
// visitor behavior) and can apply to all Captcha instances in an application 
// or be specific to a particular Captcha challenge placed on a single form. If 
// an urgent issue is ever discovered in a BotDetect sound style implementation 
// (e.g. a bug causing it to throw errors in certain circumstances, or a 
// weakness allowing some forms of automated analysis to bypass it, or a 
// memory leak etc.), users should be able to deactivate the problematic 
// SoundStyle while they're waiting for issue resolution. This BotDetect 
// setting acts as a centralized application configuration switch which allows 
// such sound style deactivation, without requiring users to examine and 
// possibly modify all of their source code that might be affected. It also 
// makes it much easier to revert the change later when the issue gets fixed.
$BotDetect->DisabledSoundStyles = 'RedAlert,HiveMind';


// Captcha localization & locale-dependent strings
// ---------------------------------------------------------------------------

// Captcha locale string, determining the exact character set used for random 
// Captcha code generation and the pronunciation language used for sound 
// Captcha generation.
// The default value is en-US.
// Valid user Captcha locale setting values are composed of ISO language codes 
// (for example en, ru, cmn, ...), charset codes (for example ja-Hira uses 
// Japanese Hiragana characters, while ja-Kana uses Japanese Katakana characters) 
// and country codes (for example en-US and en-GB differ in the pronunciation 
// used).
// Check the BotDetect localization page to find the list of currently supported 
// locales, and download the pronunciation resources required for Captcha sounds.
// If you use a right-to-left locale setting like Arabic or Hebrew, you should 
// also set the appropriate text direction on the textbox element used for 
// Captcha code retyping (dir="rtl").
$BotDetect->Locale = 'en-US';

// The alternative text of the Captcha image Html element.
// The default value is Retype the CAPTCHA code from the image.
// Valid user Captcha image tooltip setting values are arbitrary strings.
$BotDetect->ImageTooltip = 'Custom Captcha image tooltip';

// Tooltip of the Captcha sound icon.
// The default value is "Speak the CAPTCHA code".
// Valid user Captcha sound tooltip setting values are arbitrary strings.
$BotDetect->SoundTooltip = 'Custom Captcha sound icon tooltip';

// Tooltip of the Captcha reload icon.
// The default value is "Change the CAPTCHA code".
// Valid user Captcha reload tooltip setting values are arbitrary strings.
$BotDetect->ReloadTooltip = 'Custom Captcha reload icon tooltip';

// Text or tooltip of the Captcha help link, depending on help link mode.
// The default value depends on the width of the Captcha image.
// Valid user Captcha help link setting values are strings at least 4 characters 
// long.
$BotDetect->HelpLinkText = 'Custom Captcha help link text';

// Url of the localized Captcha help page the help link points to.
// The default value depends on Captcha locale.
// Valid user Captcha help link url setting values are absolute or relative Urls.
// This setting is only supported in paid versions of BotDetect.
$BotDetect->HelpLinkUrl = 'custom-captcha-help-page.html';


// Captcha controls & appearance
// ---------------------------------------------------------------------------

// Is Captcha reloading (changing the Captcha code because the current one is 
// too hard to read) enabled.
// The default value is true.
// Valid user Captcha reload enabled setting values are booleans.
// Requesting a new Captcha challenge on the current form requires client-side 
// scripting, so the reload icon is only shown in browsers that have JavaScript 
// enabled. When JavaScript is disabled or unsupported, the visitor can still 
// get a different Captcha challenge by reloading the form.
$BotDetect->ReloadEnabled = false;

// Default BotDetect Captcha icons are 22x22 pixels large, but there is also a 
// smaller set of 17x17 px icons used when the default ones are too large. 
// This settings allows you to control which icon set will be used.
// The default value is true when the Captcha image height is < 50px, and false 
// otherwise.
// Valid user use small Captcha icons setting values are booleans: setting this 
// value to true will force BotDetect to use small built-in icons, while false 
// will disable automatic switching to small icons depending on image height.
// This setting only applies to default BotDetect icons, and should not be used 
// in combination with user-defined icons.
$BotDetect->UseSmallIcons = false;

// BotDetect displays the Captcha sound and reload icon one below the other by 
// default, and switches to displaying them one beside the other when Captcha 
// images are small enough. This setting allows you to control which BotDetect 
// icon layout will be used.
// The default value is true when the Captcha image height is <40px, and false 
// otherwise.
// Valid user use horizontal Captcha icons setting values are booleans: setting 
// this value to true will force BotDetect to use a horizontal icon layout, 
// while false will disable automatic switching to horizontal icons depending 
// on image height.
// This setting only applies to default BotDetect icons, and should not be used 
// in combination with user-defined icons.
$BotDetect->UseHorizontalIcons = false;

// Url of the optional custom Captcha sound icon that will be used instead of 
// the default one.
// The default value is 'botdetect/public/bdc-sound-icon.gif'.
// Valid user Captcha sound icon setting values are absolute or relative Urls.
// When specifying a custom Captcha sound icon, you should make sure its 
// filename includes "icon", and also provide a disabled variation of the icon 
// that will be shown during sound playback (to prevent the user from clicking 
// the icon multiple times). The disabled sound icon variant should be the same 
// size and have a filename based on the active one ("icon" replaced with 
// "disabled-icon").
$BotDetect->SoundIconUrl = 'custom-sound-icon.gif';

// Url of the optional custom Captcha reload icon that will be used instead of 
// the default one.
// The default value is 'botdetect/public/bdc-reload-icon.gif'.
// Valid user Captcha reload icon setting values are absolute or relative Urls.
// When specifying a custom Captcha reload icon, you should make sure its 
// filename includes "icon", and also provide a disabled variation of the icon 
// that will be shown while the browser is waiting to fetch a new Captcha 
// challenge from the server (to prevent the user from clicking the icon
// multiple times). The disabled reload icon variant should be the same size 
// and have a filename based on the active one ("icon" replaced with 
// "disabled-icon").
$BotDetect->ReloadIconUrl = BDC_URL_ROOT . 'bdc-reload-icon.gif';

// Custom width of the Captcha icons div element.
// The default value depends on Captcha image height, since BotDetect will 
// automatically determine default icon size and position to match it.
// Valid user Captcha icons div width setting values are positive integers.
// If your custom Captcha icons are not of the same size as the default 
// BotDetect ones (22x22 px), the UseHorizontalIcons setting won't be able to 
// control the icon layout correctly. You can control whether your custom icons 
// will be displayed one beneath the other or one beside the other by setting 
// an appropriate icons div width: setting it to at least twice the icon width 
// + 8px of padding will result in horizontal icon layout, while smaller values 
// will result in vertical icon layout.
$BotDetect->IconsDivWidth = 25;

// Will Captcha markup include a link to a Captcha help page providing Captcha 
// instructions and explanations for form users.
// The default value is true.
// Valid user help link enabled setting values are booleans.
// This setting is only supported in paid versions of BotDetect.
$BotDetect->HelpLinkEnabled = true;

// How will the Captcha help link be displayed.
// The default value is Text.
// Valid user Captcha help link mode setting values are members of the 
// BotDetect HelpLinkMode enumeration ("Image" or "Text").
// When using the Image help link mode, Captcha image is wrapped in a link, and 
// clicking it opens the help page in a new browser tab. This mode takes less 
// space, but can lead to accidental clicks (particularly by mobile visitors).
// When using the Text help link mode, Captcha image height is automatically 
// reduced by 10 px and a text link to the Captcha help page is inserted below 
// it. If this makes the Captcha images less readable, you can compensate by 
// increasing the Captcha image height.
$BotDetect->HelpLinkMode = HelpLinkMode::Text;

// User-defined CSS classes that will be added to the BotDetect CAPTCHA 
// container <div>.
// The default value is empty.
// Valid user additional Css classes setting values are strings containing 
// desired class names in standard space-delimited CSS class format.
// CSS style declarations for these custom classes must be defined in a user 
// stylesheet added to the page.
$BotDetect->AdditionalCssClasses = 'class1 class2 class3';

// User-defined CSS style declarations that will be added as inline style 
// of the BotDetect CAPTCHA container <div>.
// The default value is empty.
// Valid user additional Css style setting values are strings containing 
// desired CSS style declarations in standard semicolon-delimited CSS style format.
$BotDetect->AdditionalInlineCss = 'border: 4px solid #fff; background-color: #f8f8f8;';



// Captcha client-side
// ---------------------------------------------------------------------------

// Should the BotDetect JavaScript client-side script code be included by the 
// generated Captcha container markup. 
// The default value is true.
// Valid user add script include setting values are booleans.
// This setting will usually only be set to false if you have multiple Captcha 
// instances on the same form and only want the first one's markup to include 
// the required BotDetect client-side code. Another possible use is when you 
// manually add the necessary <script> include to page <head>, possibly combined 
// with other JavaScript code and minified to reduce the number of Http requests 
// made by the page.
$BotDetect->AddScriptInclude = false;

// Should the JavaScript code for BotDetect client-side object creation be 
// included in the generated Captcha container markup.
// The default value is true.
// Valid user add init script setting values are booleans.
// Adding the initialization script fragment should be turned off only if you 
// will manually add the necessary <script> code to form <head> for example.
$BotDetect->AddInitScript = true;

// Should user Captcha code input be automatically uppercased on the fly.
// The default value is true.
// Valid user auto uppercase input setting values are booleans.
// Since Captcha validation is not and should not be case-sensitive (it would 
// hinder human visitors more than bots, and how would case differences be 
// communicated through audio Captcha in all supported pronunciation languages?), 
// automatically uppercasing user input is a small usability improvement that 
// helps communicate the case-insensitivity of the Captcha challenge to users.
$BotDetect->AutoUppercaseInput = true;

// Should the Captcha code input textbox automatically be assigned focus on 
// all Captcha sound and Captcha reload icon clicks, allowing the users to 
// more easily type in the code as they hear it or as the new image loads. 
// The default value is true.
// Valid user Captcha auto focus input setting values are booleans.
// Automatic input element focusing is not triggered by auto-reloading of 
// expired Captcha challenges, since the user might be filling out another 
// field on the form when the auto-reload starts and shouldn't be distracted.
$BotDetect->AutoFocusInput = true;

// Should the Captcha user input textbox automatically be cleared on all 
// reload icon clicks and auto-reloads of expired Captcha codes.
// The default value is true.
// Valid user auto clear input setting values are booleans.
// Automatic input clearing is a small usability improvement: since any 
// previous user input will be invalidated by Captcha reloading, it helps so 
// users don't have to delete the previous input themselves.
$BotDetect->AutoClearInput = true;

// Should Captcha challenges automatically be reloaded when the Captcha code 
// expires (controlled by the CodeTimeout property).
// The default value is true.
// Valid user auto reload expired Captchas setting values are booleans.
// Automatic reloading of expired Captcha codes allows you to have a short 
// Captcha code timeout (e.g. 2 minutes) to narrow the window of opportunity 
// for Captcha reusing on other sites or human-solver-powered bots, and actual 
// visitors can still fill out your form at their own pace and without rushing 
// (since the Captcha image will be reloaded automatically when it is no longer 
// valid).
$BotDetect->AutoReloadExpiredCaptchas = true;

// Time period in seconds after which automatic reloading of expired Captcha 
// challenges will cease.
// The default value is 7200 seconds (2 hours).
// Valid user auto reload timeout setting values are positive integers.
// This timeout prevents indefinite extension of the visitor Session, when the 
// user leaves the form open in a background browser tab over the weekend for 
// example.
$BotDetect->AutoReloadTimeout = 3600; // 1 hour

// Starting delay (in milliseconds) of Captcha audio JavaScript playback.
// The default value is 0 (no delay).
// Valid user Captcha sound start delay setting values are positive integers.
// An initial delay before browser sound playback can be useful for improving 
// usability of the Captcha audio for blind people using JAWS or similar screen 
// readers. Such assistive technology will read the label associated with the 
// Captcha code textbox and start sound playback simultaneously when the sound 
// icon is activated (since Captcha sound playing automatically focuses the 
// Captcha code textbox by default). Setting this delay to e.g. 2000 (2 seconds) 
// will give the user time to hear both the pronounced label and the Captcha 
// sound clearly.
$BotDetect->SoundStartDelay = 1000;

// Should BotDetect also add a remote JavaScript include 
// (remote.captcha.com/include.js) loaded from the captcha.com server (which is 
// currently used only for stats, but is planned to develop into additional 
// Captcha functionality).
// The default value is true.
// Valid user remote script enabled setting values are booleans.
// This setting is only supported in paid versions of BotDetct.
$BotDetect->RemoteScriptEnabled = true;



// Captcha-related PHP application settings
// ---------------------------------------------------------------------------

// The Url of the PHP script processing Captcha challenge Http requests.
// The default value is "botdetect.php".
// Valid user Captcha handler Url setting values are strings containing Url 
// paths.
// If you need to implement a custom handler for Captcha requests (for example, 
// to conform to conventions of a MVC framework), you can change the base Url 
// of Captcha image/sound/validation requests through the HandlerUrl 
// configuration property. You will of course also have to implement the 
// BotDetect Captcha library initialization (usually performed by botdetect.php) 
// in your custom handler .php source.
$BotDetect->HandlerUrl = 'custom-captcha-request-handler.php';

// Functions used by BotDetect to store Captcha codes and other Captcha data 
// between Http requests.
// The default values are names of built-in BotDetect functions wrapping access 
// to PHP Session state ('PHP_Session_Save', 'PHP_Session_Load', 
// 'PHP_Session_Clear').
// Valid user Captcha persistence function names setting values are strings with 
// names of defined Save($key, $value) / Load($key) / Clear($key) functions.
// BotDetect requires server-side storage to persist Captcha codes and other 
// Captcha data across Http requests (so the Captcha code generated during the 
// Captcha image GET request can be compared to user input when processing the 
// form POST request etc.). In case you want to use a custom storage medium for 
// Captcha data in your website (e.g. a database), you can use this BotDetect 
// setting to customize the persistence back end used by BotDetect code.
// Please note that BotDetect code calls these persistence function when the 
// Captcha generation & validation workflow requires it, and doesn't know the 
// details of the underlying persistence medium. Due to the nature of the data 
// stored (Captcha codes & similar), the persistence medium should be 
// visitor-specific and automatically cleared when a "visit" ends (just like 
// PHP Sessions are).
// In your implementation, you should take care that data is kept separate for 
// different visitors (so any Captcha code can be validated only by the same 
// visitor that caused it to be generated in the first place – otherwise you'd 
// reduce Captcha security), and cleared when appropriate (if you just save 
// Captcha data in a Session-like SQL database but never clear it, the database 
// will grow in size infinitely!).
$BotDetect->SaveFunctionName = 'PHP_Session_Save';
$BotDetect->LoadFunctionName = 'PHP_Session_Load';
$BotDetect->ClearFunctionName = 'PHP_Session_Clear';

?>

Since the code example includes the BotDetect Captcha library from a shared location, we use a local config file to override base Captcha settings. If you are just copying the whole Captcha library to the root folder of your website, you could make the same changes which are described at the Captcha configuration options page .

The example CaptchaConfig.php file shows and explains most Captcha configuration settings available.