title: Add data dynamically to an Array
body: <p>I want to add data to an array dynamically. How can I do that? Example</p>
  <pre><code>$arr1 = [
      'aaa',
      'bbb',
      'ccc',
  ];
  // How can I now add another value?
  
  $arr2 = [
      'A' =&gt; 'aaa',
      'B' =&gt; 'bbb',
      'C' =&gt; 'ccc',
  ];
  // How can I now add a D?
  </code></pre>