Gravity Forms Spam Prevention

gf-spam-prevent.php

<?php
/**
 * SPAM filtering function
 *
 * @param string[] $result Current Result. Contains two keys 'is_valid' and 'message'.
 * @param mixed    $value  Field value -could be string or string[].
 * @param array    $form   Form Entity.
 * @param array    $field  Field Entity.
 *
 * @return array
 */
function esch_spam_validation_prevent( array $result, $value, $form, $field ): array {

	$invalid_triggers = [
		'cialis'       => [],
		'viagra'       => [],
		'levitra'      => [],
		'essay'        => [],
		'.ru'          => [],
		'.xyz'         => [],
		'.online'      => [],
		'pharmacy.com' => [],
		'doxycycline'  => [],
		'д'            => [],
		'.wiki'        => [],
		'google'       => [],
		'me photo'     => [],
		'http'         => [ 'name' ],
	];

	/**
	 * Invalid RegEx
	 *
	 * @var $invalid_regexes
	 */
	$invalid_regexes = [
		"/^Mel(\W+|$)/"
	];

	/**
	 * First find any NOT specific to any field.
	 */
	$universal_invalid = array_filter( $invalid_triggers, function ( $value ) {
		return $value == [];
	} );

	str_ireplace( array_keys( $universal_invalid ), '', $value, $count );

	/**
	 * Second, check field specific.
	 */
	$field_specific_invalid = array_filter( $invalid_triggers );

	foreach ( $field_specific_invalid as $invalid_string => $applicable_fields ) {
		if ( in_array( $field['type'], $applicable_fields, true ) ) {
			str_ireplace( $invalid_string, '', $value, $invalid_specific_count );
			$count += $invalid_specific_count;
		}
	}

	/**
	 * Finally, check regexes.
	 */
	foreach ( $invalid_regexes as $invalid_regex ) {
		if ( is_string( $value ) ) {
			if ( preg_match( $invalid_regex, $value ) ) {
				$count++;
			}
		} else {
			foreach ( $value as $field_part ) {
				if ( preg_match( $invalid_regex, $field_part ) ) {
					$count++;
				}
			}
		}
	}

	if ( $count > 0 ) {
		$result['is_valid'] = false;
		$result['message']  = sprintf(
			'This field contains %d word%s associated with SPAM. Please check your submission and try again.',
			$count,
			$count !== 1 ? 's' : '',
		);
	}

	return $result;
}

add_filter( 'gform_field_validation', 'esch_spam_validation_prevent', 10, 4 );