Adding an anti-spam question to subscription form

Hi Comrade, in EasyMail you can add custom fields using some hooks:
https://www.eventualo.net/blog/easymail-newsletter-for-developers/#tutorial-customfields
I wrote some code for you. It’s a draft starting point to show the hooks you can use. In this sample I set a global var ($alo_em_captcha) and I use it to (potentially) create a captcha and check the submitted value. You have to make all the hard work, mine it’s just a suggestion… I hope it helps you.

/**
 * Add a captcha input field in subscription form
 */
function custom_easymail_add_captcha ( $fields ) {

	global $alo_em_captcha;

	// Set a captcha global variable you can use to verify
	// e.g. it could be an array with more parameters
	$alo_em_captcha = rand( 1, 1000 );

	// Custom field: Captcha
	$fields['cf_captcha'] = array(
		'humans_name'		=> __("CAPTCHA", "alo-easymail"),
		'sql_attr' 			=> "VARCHAR(1) NOT NULL",
		'input_type' 		=> "text",
		'input_mandatory' 	=> true,
		'input_validation' 	=> 'custom_easymail_cf_check_captcha',
		'input_attr'		=> ' maxlength="20" '
	);

	return $fields;
}
add_filter ( 'alo_easymail_newsletter_set_custom_fields', 'custom_easymail_add_captcha' );

/**
 * Sample of validation function
 */
function custom_easymail_cf_check_captcha ($data) {
	global $alo_em_captcha;

	// check the submitted $data in captcha against a value based on $alo_em_captcha, and return true or false
}

/**
 * If your captcha needs some javascript, you can add it in your theme footer
 */
function custom_easymail_add_captcha_js ( $fields ) {
	global $alo_em_captcha; ?>
<script type="text/javascript">
//<![CDATA[

// create your captcha javascript here, based on $alo_em_captcha:
// <?php echo $alo_em_captcha; ?>

//]]>
</script>
<?php
}
add_action ( 'wp_footer', 'custom_easymail_add_captcha_js' );

/**
 * You can translate the captcha label, based on $alo_em_captcha
 */
function custom_easymail_gettext ( $translated_text, $untranslated_text, $domain ) {
	global $alo_em_captcha;

	if ( $untranslated_text === 'CAPTCHA' && $domain == "alo-easymail" ) {

		// Set the question text, based on $alo_em_captcha
		return __('Your captcha question...'). $alo_em_captcha;

	}
	return $translated_text;
}
add_filter('gettext', 'custom_easymail_gettext', 20, 3);

Thanks! I had looked at the custom field stuff prior to posting my original question and didn’t think it would work, but now that I’m looking at your code I really don’t know what I was thinking. :-/ Anyway your solution works perfectly just like your documentation says. Here is the code that I used:

/**
 * Add an anti-spam question to Easymail newsletter subscription form
 */
function easymail_add_antispam ( $fields ) {

	// Custom field: Captcha
	$fields['cf_captcha'] = array(
		'humans_name'		=> __("What color is an orange?", "alo-easymail"),
		'sql_attr' 			=> "VARCHAR(1) NOT NULL",
		'input_type' 		=> "text",
		'input_mandatory' 	=> true,
		'input_validation' 	=> 'easymail_validate_antispam',
		'input_attr'		=> ' maxlength="20" '
	);

	return $fields;
}
add_filter ( 'alo_easymail_newsletter_set_custom_fields', 'easymail_add_antispam' );

/**
 * Validate input of antispam question
 */
function easymail_validate_antispam ($data) {
	$text = strtolower($data);
	if ($text == 'orange')
		return true;
	else
		return false;
}