We had a user who was using a custom text field with the HTML5 validation as a sort of invite code system. The issue was that bots can easily bypass HTML5 validation, so some server-side validation is also needed. This is a short tutorial on how to implement custom server side validation for a custom field.

First, Add a Custom Text Field

Go to UsersWP > Form Builder > Add a text field.
Make sure you note the “Key” in this case “invite_code”.

Here, I have not added any HTML5 validation as it is not required if we are doing server-side validation.

Add the field to the register form

Above, I have set this to “Include this field ONLY in the register form”.

Go to UsersWP > Form Builder > Register > Add the new field to the register form and drag it where you want it to show, I have added it as the first field.

Add the server-side validation

Below we add a code snippet to validate the invite code, note that the “invite_code” key used has to match the field Key. We have a list of valid invite codes, this list can be as long or short as needed.

add_filter('uwp_validate_fields_before','_my_invite_code_check',10,3);
function _my_invite_code_check( $errors, $data, $type ){
	
	// List of valid codes
	$valid_codes = array(
		'SAMPLE123',
		'CAT345',
		'BOB99',
		'123456',
		'POOL'
	);
	

	// only run chcks if we have data and its a register call
	if (!empty($data) && $type === 'register') {
		
		// if empty add an error
		if(empty($data['invite_code'])){
			 $errors->add('not_logged_in', __('<strong>Error</strong>: Invite Code Empty', 'userswp'));
		}elseif(!in_array($data['invite_code'],$valid_codes)){
			// if used code is not in our list then add an error
			$errors->add('not_logged_in', __('<strong>Error</strong>: Invite Code Not Valid', 'userswp'));
		}
		
	}
	
	return $errors;
}

Result

Users will only be able to register if they have a valid invite code.