source: http://docs.buddyforms.com/article/402-validation

validation.php

 <?php
    //----------AFTER THE FORM HAS BEEN SUBMITTED----------
    include("PFBC/Form.php");
    if(!Form::isValid("<replace with unique form identifier>")) {
        /* Validation errors have been found.  We now need to redirect users back to the 
        form back so the errors can be corrected and the form can be re-submitted.
           In case of ajax submit Form::renderAjaxErrorResponse () will build an error reply.*/

        if ($reqIs("AJAX")) {
            header ("Content-type: application/json");
            Form::renderAjaxErrorResponse($formName);
        } else
            header("Location: <replace with form url>");
    }
    //form submitted data has been validated.  Your script can now proceed with any further processing required.*/   

// Custom Validation
// Often times, you'll find that you need to apply custom validation to your forms' submitted data. For instance, if you create a login form, you'll need to validate user entered credentials against your system. PHP-Bootstrap-Form has several methods that support this type of scenario. Let's take a look at an example implementation.

//----------AFTER THE FORM HAS BEEN SUBMITTED----------
include("PFBC/Form.php");
if(Form::isValid("login", false)) {
    if(isValidUser($_POST["Email"], $_POST["Password"])) {
        Form::clearValues("login");
        header("Location: profile.php");
    }
    else {
        Form::setError("login", "Error: Invalid Email Address / Password");
        header("Location: login.php");
    }
}
else
    header("Location: login.php");