[Indikator Design - EMP License Key Registration] Needs to run in WordPress

class-license.php

<?php
/**
 * Do not allow direct access
 *
 * @since    1.0.0
 */
if ( ! defined( 'ABSPATH' ) ) die( 'Don\'t try to load this file directly!' );

/**
 * Indikator Design - EMP License Key Registration
 *
 * @since    1.0.0
 */
if ( ! class_exists( 'IdLicenseKeyRegistration' ) )
{

    class IdLicenseKeyRegistration
    {

        /**
         * Define properties
         *
         * @since    1.0.0
         */
        private $id;

        private $key;

        private $email;

        private $secret;

        private $vector;

        /**
         * Constructor
         *
         * @since    1.0.0
         */
        public function __construct( $id, $email, $key )
        {

            $this->id     = 'id';

            $this->key    = 'key';

            $this->email  = 'email';

            $this->secret = 'your-key'; // Get your key from your EMP Profile Page

            $this->vector = 'your-vector'; // Get your vector from your EMP Profile Page

            /**
             * Let the magic happens
             *
             * @since 1.0.0
             */
            $this->initialize();

        } // end constructor

        /**********************************************************************************
            Check the license object and create a user
        **********************************************************************************/

        /**
         * Initialize
         *
         * @since 1.0.0
         */
        public function initialize()
        {

            $obj = $this->getLicenseObj( $this->key, $this->id, $this->email );

            if ( is_object( $obj ) )
                $id = $this->create( $obj );

            if ( is_int( $id ) )
            {

                // return do something

            } // end if

            // return do something else

        } // end initialize

        /**********************************************************************************
            Methods related to the license
        **********************************************************************************/

        /**
         * Get the license information
         *
         * @since 1.0.0
         */
        public function getLicenseObj( $key, $id, $email )
        {

            $obj = json_decode( $this->processKey( $this->secret, $this->vector, $key, true ) );

            if ( is_object( $obj ) )
            {

                $obj = (object) $this->sanitizeArr( (array) $obj );

                return $this->verifyLicense( $obj, $id, $email );

            } // end if

            return false;

        } // end getLicenseObj

        /**
         * Encrypt/Decrypt the customer secret credential key
         *
         * @since 1.0.0
         */
        private function processKey( $key, $vec, $data, $decrypt = false )
        {

            $met = 'AES-256-CBC';
            $key = hash( 'sha256', $key );
            $vec = substr( hash( 'sha256', $vec ), 0, 16 );

            if ( ! $decrypt )
                return base64_encode( openssl_encrypt( $data, $met, $key, 0, $vec ) );

            else
                   return openssl_decrypt( base64_decode( $data ), $met, $key, 0, $vec );

        } // end processKey

        /**
         * Check the license information
         *
         * @since 1.0.0
         */
        private function verifyLicense( $obj, $id, $email )
        {

            if ( (int) $obj->payID != (int) $id || $obj->email != $email )
                return false;

            return $obj;

        } // end verifyLicense

        /**
         * Sanitize multidimensional Arrays
         *
         * @since 1.0.0
         */
        public function sanitizeArr( $arr )
        {

            foreach( $arr as $key => $val )
            {

                if ( false !== strpos( $key, 'key' ) || false !== strpos( $key, 'pass' ) )
                {

                    $arr[$key] = $val;

                    continue;

                } // end if

                if ( false !== strpos( $key, 'url' ) || false !== strpos( $val, '//:' ) )
                {

                    $arr[$key] = esc_url_raw( $val );

                    continue;

                } // end if

                $arr[$key] = esc_attr( $val );

            } // end foreach

            return $arr;

        } // end sanitizeArr

        /**********************************************************************************
            Methods related to the user creation
        **********************************************************************************/

        /**
         * Create User
         *
         * @since 1.0.0
         */
        public function create( $obj )
        {

            $id = wp_insert_user(
            [

                'user_pass'     => $obj->pass,
                'user_login'    => isset( $obj->user ) ? $obj->user : $obj->email,
                'user_email'    => $obj->email,
                'first_name'    => isset( $obj->first ) ? $obj->first : '',
                'last_name'     => isset( $obj->last )  ? $obj->last  : '',
                'nickname'      => isset( $obj->first, $obj->last ) ? $obj->first . ' ' . $obj->last : '',
                'display_name'  => isset( $obj->first, $obj->last ) ? $obj->first . ' ' . $obj->last : '',
                'role'          => 'subscriber', // Set your desired user role

            ]); // end $user

            if ( is_int( $id ) )
            {

                $this->setLicense( $id, $obj );

            } // end if

            return $id;

        } // end create

        /**
         * Set the license key
         *
         * @since 1.0.0
         */
        public function setLicense( $id, $obj )
        {

              // Add your desired Meta Key here
            $key  = '_license_' . str_replace( ' ', '_', strtolower( $obj->market ) ) . '_' . $obj->itemID;

            $meta = get_user_meta( $id, $key, true );

            $date = strtotime( $obj->date );

            $expr = $this->expirationDate( $obj->expire, $date, $obj );

            if ( time() >= $expr )
                return false; // Do something if the license is expired

            if ( $meta && ( (int) $meta->expire === $expr ) )
                return false; // Do something if the license is already added

            if ( $meta && ( (int) $meta->expire > $expr ) )
                return false; // Do something if a newer license is already added

            return update_user_meta( $id, $key, (object)
            [

                'expire' => $expr,
                'payID'  => (int) $obj->payID,
                'itemID' => (int) $obj->itemID,
                'market' => $obj->market,
                'author' => $obj->author,
                'title'  => $obj->title,
                'email'  => $obj->email,
                'date'   => $date,

            ]); // end update_user_meta

        } // end setLicense

        /**
         * Determining the expiration date
         *
         * @since 1.0.0
         */
        public function expirationDate( $expire, $date, $obj )
        {

            return ( 'lifetime' == $expire || '' == $expire ) ? (int) $date + ( 100 * YEAR_IN_SECONDS ) : (int) $expire;

        } // end expirationDate
    } // end class
} // end if

// Instantiate the class
new IdLicenseKeyRegistration( $id, $email, $key );