vBulletin 3.6 - Register new user from outside vbulletin directory

[Nullifi3d]

I am trying to implement a script that adds a new vbulletin user during a shopping cart purchase within the WHMCS cart page. I have the basic jquery script built to check for username availability and it's setup for user insertion.

I just need to know what the minimum user variables are that need to be included during sql injection, as well as what validations I may need to use to ensure no vbulletin errors occur. I am using vBulletin 3.6 and the current code I am using in my WHMCS shopping cart is below:

JS Code:

PHP Code:

jQuery(document).ready(function(){
    jQuery("#customfield2").keyup(function() {
        var cfvalue = jQuery("#customfield2").val();
        setTimeout(function() {
            if (cfvalue != jQuery("#customfield2").val()) {return;}
            jQuery("#cf2").attr("src","images/custom/icons/hourglass.gif");
            if (cfvalue == '') {
                jQuery("#cf2").hide();
            } else if (cfvalue != '') {
                jQuery("#cf2").show();
                checkAvailability(cfvalue);
            }
        }, 1000);
    });
});

function checkAvailability(cf2){
    $.post("includes/vbusername.php", {task: "check", username: cf2}, function(result) {
        jQuery("#cf2").attr("src",(result == 'available' ? 'images/custom/icons/check.gif' : 'images/custom/icons/x.gif'));
    });
}

function createUser(cf2){
    $.post("includes/vbusername.php", {task: "create", username: cf2});
}

function showUsernameNotification() {
    document.write('<img src="images/custom/icons/hourglass.gif" alt="-" border="0" id="cf2" style="margin-bottom: -8px;" /> ');
    jQuery("#cf2").hide();
} 


PHP Code:

<?php

// ####################### SET PHP ENVIRONMENT ###########################
error_reporting(E_ALL & ~E_NOTICE);

// #################### DEFINE IMPORTANT CONSTANTS #######################
define('THIS_SCRIPT', 'vbusername');

// ######################### REQUIRE BACK-END ############################
chdir('/home/********/public_html/community');
require_once('./global.php');
require_once(DIR . '/includes/functions_user.php');
require_once(DIR . '/includes/functions_misc.php');

// #######################################################################
// ######################## START MAIN SCRIPT ############################
// #######################################################################

$vbulletin->GPC['username'] = mysql_real_escape_string($_POST['username']);

if ($_POST['task'] == "check") {
    if ($db->query_first("SELECT username FROM ".TABLE_PREFIX."user WHERE username = '".$vbulletin->GPC['username']."'")) {echo "unavailable";} else {echo "available";}
}

if ($_POST['task'] == "create") {
    $vbulletin->input->clean_array_gpc('p', array(
        'options'             => TYPE_ARRAY_BOOL,
        'username'            => TYPE_STR,
        'email'               => TYPE_STR,
        'emailconfirm'        => TYPE_STR,
        'parentemail'         => TYPE_STR,
        'password'            => TYPE_STR,
        'password_md5'        => TYPE_STR,
        'passwordconfirm'     => TYPE_STR,
        'passwordconfirm_md5' => TYPE_STR,
        'referrername'        => TYPE_NOHTML,
        'imagestamp'          => TYPE_STR,
        'imagehash'           => TYPE_STR,
        'coppauser'           => TYPE_BOOL,
        'day'                 => TYPE_UINT,
        'month'               => TYPE_UINT,
        'year'                => TYPE_UINT,
        'timezoneoffset'      => TYPE_NUM,
        'dst'                 => TYPE_UINT,
        'userfield'           => TYPE_ARRAY,
        'showbirthday'        => TYPE_UINT,
    ));

    $userdata =& datamanager_init('User', $vbulletin, ERRTYPE_ARRAY);

    $userdata->set_info('coppauser', $vbulletin->GPC['coppauser']);
    $userdata->set_info('coppapassword', $vbulletin->GPC['password']);
    $userdata->set_bitfield('options', 'coppauser', $vbulletin->GPC['coppauser']);
    $userdata->set('parentemail', $vbulletin->GPC['parentemail']);
    $userdata->set('password', ($vbulletin->GPC['password_md5'] ? $vbulletin->GPC['password_md5'] : $vbulletin->GPC['password']));
    $userdata->set('email', $vbulletin->GPC['email']);
    $userdata->set('username', $vbulletin->GPC['username']);
    $userdata->set('referrerid', $vbulletin->GPC['referrername']);
    if ($vbulletin->options['verifyemail']) {$newusergroupid = 3;}
    else if ($vbulletin->options['moderatenewmembers'] OR $vbulletin->GPC['coppauser']) {$newusergroupid = 4;}
    else {$newusergroupid = 2;}
    $userdata->set('usergroupid', $newusergroupid);
    $userdata->set('languageid', $vbulletin->userinfo['languageid']);
    $userdata->set_usertitle('', false, $vbulletin->usergroupcache["$newusergroupid"], false, false);
    $userdata->set('showbirthday', $vbulletin->GPC['showbirthday']);
    $userdata->set('birthday', array(
        'day'   => $vbulletin->GPC['day'],
        'month' => $vbulletin->GPC['month'],
        'year'  => $vbulletin->GPC['year']
    ));
    $userdata->set_dst($vbulletin->GPC['dst']);
    $userdata->set('timezoneoffset', $vbulletin->GPC['timezoneoffset']);
    $userdata->set('ipaddress', IPADDRESS);
    $userdata->pre_save();
    $vbulletin->userinfo['userid']
        = $userid
        = $userdata->save();    
}

?>

[Nullifi3d]

Can anyone give me any guidance on the minimum tables/fields that need to be inserted when creating a new user? I am simply trying to insert users from my shopping cart pages, but want to ensure that I am inserting what I need to and utilizing proper validation methods.