title: Implement PhpSpreadsheet in Codeigniter 4
body: <p>i am really a beginner and i am trying to install PhpSpreadsheet in Codeigniter 4 in the ThirdParty folder.
  The instructions I find going around the net refer to &quot;composer&quot; but I have no idea how to run this command (I'm in Windows 10, XAMPP, Codeigniter 4.1.1 and PHP 7.3).
  I would still like to install everything manually.</p>
  <p>So I proceeded like this:</p>
  <ul>
  <li>In the ThirdParty folder I created a PhpOffice folder and downloaded the contents of PhpSpreadsheet.</li>
  <li>I then modified the Autoload.php file (from the codeigniter app/Config folder) in this way:</li>
  </ul>
  <p>public $psr4 = [</p>
  <pre><code>APP_NAMESPACE =&gt; APPPATH, // For custom app namespace
  
  'Config'      =&gt; APPPATH . 'Config',
  
  'PhpOffice\PhpSpreadsheet' =&gt; APPPATH . 'ThirdParty/PhpOffice/PhpSpreadsheet', 
  </code></pre>
  <p>];</p>
  <p>Then I created the Example.php controller like so:</p>
  <pre><code>&lt;? php
  namespace App\Controllers;
  
  use \PhpOffice\PhpSpreadsheet\Spreadsheet;
  use \PhpOffice\PhpSpreadsheet\Writer\Xlsx;
  
  class Example extends BaseController
  {
      public function index ()
      {
          $ spreadsheet = new Spreadsheet ();
      }
  }
  </code></pre>
  <p>Well this line of code alone generates the following error:</p>
  <p>Error</p>
  <p>Interface 'Psr \ SimpleCache \ CacheInterface' not found</p>
  <p>APPPATH \ ThirdParty \ PhpOffice \ PhpSpreadsheet \ Collection \ Memory.php at line 13</p>
  <p>I have no idea how to fix.
  Thanks in advance to all those who will answer</p>