Adds a class that defines the type of field to the <li> element in Gravity Forms

add-field-type-to-class.php

<?php
add_filter( 'gform_field_css_class', 'cameronjonesweb_add_field_type_to_class', 10, 3 );

/**
 * Adds a class that defines the type of field to the li element in Gravity Forms
 *
 * @param string   $css_class The existing CSS classes.
 * @param GF_Field $field The field object.
 * @param array    $form The form object.
 * @return string
 */
function cameronjonesweb_add_field_type_to_class( $css_class, $field, $form ) {
	$css_class .= ' gfield--' . $field->type;
	return $css_class;
};