Captcha alternative

Download and Install -> http://wordpress.org/extend/plugins/really-simple-captcha/

Copy and Modify Template File at wp-content/plugins/events-manager/templates/placeholders/bookingform.php
1. copy php file at wp-content/plugins/events-manager/templates/placeholders/bookingform.php
2. paste in your current theme directory e.g. wp-content/themes/YOUR THEME NAME/plugins/events-manager/bookingform.php (create folders if not existing)
3. open and modify

PASTE THIS SNIPPET
==================================
<?php
$captcha_instance = new ReallySimpleCaptcha();
$captcha_instance->chars = 'ABCDEFGHJKLMNPQRSTUVWXYZ23456789';
$captcha_instance->char_length = '4';
// Width/Height dimensions of CAPTCHA image.
$captcha_instance->img_size = array( '72', '24' );
// Font color of CAPTCHA characters, in RGB (0 - 255).
$captcha_instance->fg = array( '0', '0', '0' );
// Background color of CAPTCHA image, in RGB (0 - 255).
$captcha_instance->bg = array( '255', '255', '255' );
// Font Size of CAPTCHA characters.
$captcha_instance->font_size = '16';
// Width between CAPTCHA characters.
$captcha_instance->font_char_width = '15';
// CAPTCHA image type. Can be 'png', 'jpeg', or 'gif'
$captcha_instance->img_type = 'png';
$captcha_instance_word = $captcha_instance->generate_random_word();
$captcha_instance_prefix = mt_rand();
$captcha_instance_image_name = $captcha_instance->generate_image($captcha_instance_prefix, $captcha_instance_word);
$captcha_instance_image_url =  get_bloginfo('wpurl') . '/wp-content/plugins/really-simple-captcha/tmp/';
$captcha_instance_image_src = $captcha_instance_image_url.$captcha_instance_image_name;
$captcha_instance_image_width = $captcha_instance->img_size[0];
$captcha_instance_image_height = $captcha_instance->img_size[1];
$captcha_instance_field_size = $captcha_instance->char_length;
$captcha_instance_form_label = 'Anti-Spam:';
?>
<p class="comment-form-captcha">
<img src="<?php echo $captcha_instance_image_src; ?>" alt="captcha" width="<?php echo $captcha_instance_image_width; ?>" height="<?php echo $captcha_instance_image_height; ?>" />
<label for="captcha_code"><?php echo $captcha_instance_form_label; ?></label>
<input id="captcha_instance_code" name="captcha_instance_code" size="<?php echo $captcha_instance_field_size; ?>" type="text" />
<input id="captcha_instance_prefix" name="captcha_instance_prefix" type="hidden" value="<?php echo $captcha_instance_prefix; ?>" />
</p>
==================================

ABOVE
==================================
<div class="em-booking-buttons">
<?php if( preg_match('/https?:\/\//',get_option('dbem_bookings_submit_button')) ): //Settings have an image url (we assume). Use it here as the button.?>
==================================

PASTE THIS SNIPPET IN YOUR THEME FUNCTIONS.PHP
==================================
function em_validate(){
 global $EM_Event,$EM_Notices;
 $captcha_instance = new ReallySimpleCaptcha();
 $captcha_instance_correct = false;
 $captcha_instance_prefix = $_POST['captcha_instance_prefix'];
 $captcha_instance_code = $_POST['captcha_instance_code'];
 $captcha_instance_check = $captcha_instance->check( $captcha_instance_prefix, $captcha_instance_code );
 $captcha_instance_correct = $captcha_instance_check;
 if ( !$captcha_instance_correct ){
  $EM_Notices->add_error('Invalid security code');
   return false;
 }
 return true;
}
add_filter('em_event_validate','em_validate');
==================================