Gravity Forms Custom Validation

plugin-gravityforms.php

<php
/**
 * Validate Gravity Forms text and name fields.
 *
 * Rejects common gibberish patterns, repeated characters, invalid characters,
 * and values shorter than two characters.
 *
 * @since 1.6.2
 *
 * @param array $validation_result Gravity Forms validation result.
 *
 * @return array Modified Gravity Forms validation result.
 */
function wd_validate_gravity_form_fields( $validation_result ) {
	$form = $validation_result['form'];

	foreach ( $form['fields'] as &$field ) {
		// Target single-line text and name fields.
		if ( ! in_array( $field->type, array( 'text', 'name' ), true ) ) {
			continue;
		}

		$value = rgpost( 'input_' . $field->id );

		// Handle the array returned by a full name field.
		if ( is_array( $value ) ) {
			$value = implode( ' ', $value );
		}

		// Skip empty fields if they are not required.
		if ( empty( $value ) ) {
			continue;
		}

		// Block common keyboard-mashing and placeholder values.
		$gibberish_patterns = '/(asdf|qwerty|zxcv|1234|test|null|n\/a)/i';

		// Block four or more repeated consecutive characters.
		$repeated_chars = '/(.)\1{3,}/i';

		// Allow letters, whitespace, hyphens, and apostrophes only.
		$invalid_chars = '/[^\p{L}\s\-\']/u';

		// Require at least two characters.
		$is_too_short = mb_strlen( trim( $value ) ) < 2;

		if (
			preg_match( $gibberish_patterns, $value ) ||
			preg_match( $repeated_chars, $value ) ||
			preg_match( $invalid_chars, $value ) ||
			$is_too_short
		) {
			$validation_result['is_valid']     = false;
			$field->failed_validation          = true;
			$field->validation_message         = __(
				'Please enter a valid name using letters, spaces, hyphens, or apostrophes.',
				'text-domain'
			);
		}
	}

	$validation_result['form'] = $form;

	return $validation_result;
}
add_filter( 'gform_validation', __NAMESPACE__ . '\wd_validate_gravity_form_fields' );