title: Wordpress widget php file is not translatable with PO files
body: <p>Can anyone help me why these strings in the php are not translatable?
  How am I supposed to change the code, so that the &quot;Jhon&quot; &amp; &quot;Doe&quot; placeholders can be translatable using PO edit?</p>
  <pre><code>        'first_name_input'    =&gt; [
              'type'        =&gt; 'text',
              'name'        =&gt; 'first_name',
              'id'          =&gt; 'first_name' . esc_attr( $id ),
              'placeholder' =&gt; ($settings['first_name_placeholder']) ? $settings['first_name_placeholder'] : 'Jhon',
              'class'       =&gt; [
                  'first_name',
                  'bdt-input',
                  'bdt-form-' . $settings['input_size'],
              ],
          ],
          'last_name_input'     =&gt; [
              'type'        =&gt; 'text',
              'name'        =&gt; 'last_name',
              'id'          =&gt; 'last_name' . esc_attr( $id ),
              'placeholder' =&gt; ($settings['last_name_placeholder']) ? $settings['last_name_placeholder'] : 'Doe',
              'class'       =&gt; [
                  'last_name',
                  'bdt-input',
                  'bdt-form-' . $settings['input_size'],
              ],
          ],
  </code></pre>
  <p>Many thanks in advance.</p>