Gravity Forms email blacklist

gravity-forms-email-blacklist.php

add_filter( 'gform_field_validation', 'PREFIX_gravity_forms_blacklist', 10, 4 );
/**
 * Added Validation check for email vs blacklist of free email accounts.
 *
 * @param $result array         The validation result to be filtered
 * @param $value  string|array  The field value to be validated
 * @param $form   object        Current Form object
 * @param $field  object        Current Field object
 *
 * @return mixed
 */
function PREFIX_gravity_forms_blacklist( $result, $value, $form, $field ) {
	if ( $field->get_input_type() === 'email' && $result['is_valid'] ) {

		$domain    = explode( '@', $value );
		$blacklist = array(
			'gmail.com',
			'yahoo.com',
			'hotmail.com'
		);

		if ( in_array( $domain[1], $blacklist ) ) {
			$result['is_valid'] = false;
			$result['message']  = 'Please use a work email.';
		}
	}

	return $result;
}