title: Wordpress customizer - replace text in get_theme_mod
body: <p>I have footer in Wordpress theme, and in the footer paragraph.
  <br><br>
  It looks like this:</p>
  
  <pre>&lt;p&gt;&lt;?php echo get_theme_mod( 'site_intro' ); ?&gt;&lt;/p&gt;</pre>
  
  <p>And when you in customizer there is option to change text in footer.<br>
  I want to be displayed by default for example:<br>
  <b>Copyright 2014.</b></p>
  
  <p>This is default text, and if user change this, text will be <b>replace</b> Copyright 2014 and it will be text that user has setup.</p>
  
  <p>Where I need to make some code, in footer.php, functions.php where are the rest of the code for customizer?</p>
  
  <p>Is this made with if else statement, or there is some premade code in Wordpress?
  <br>
  <br></p>
  
  <p>This is functions.php<br><br></p>
  
  <pre>function theme_customize_register( $wp_customize ) {
  
      if ( class_exists( 'WP_Customize_Control' ) ) {
          class PTD_Textarea_Control extends WP_Customize_Control {
              public function render_content() {?&gt;
                  &lt;label&gt;
                  &lt;span class=&quot;customize-control-title&quot;&gt;&lt;?php echo esc_html( $this-&gt;label );?&gt;&lt;/span&gt;
                  &lt;textarea class=&quot;large-text&quot; cols=&quot;20&quot; rows=&quot;5&quot; &lt;?php $this-&gt;link(); ?&gt;&gt;
                      &lt;?php echo esc_textarea( $this-&gt;value() ); ?&gt;
                  &lt;/textarea&gt;
                  &lt;/label&gt;
                  &lt;?php
              }
          }
      }
  
      $wp_customize-&gt;add_setting( 'site_intro', array(
          'default'           =&gt; '',
          'transport'         =&gt; 'postMessage'
      ));
      $wp_customize-&gt;add_section( 'theme_site_info', array(
          'title'             =&gt; 'Footer informaation', 'theme',
          'description'       =&gt; 'Custom Footer', 'theme',
          'priority'          =&gt; 20,
      ));
      $wp_customize-&gt;add_control( new PTD_Textarea_Control( $wp_customize, 'site_intro_control', array(
          'label'             =&gt; 'Website Footer', 'theme',
          'section'           =&gt; 'theme_site_info',
          'settings'          =&gt; 'site_intro'
      )));
  
  }
  add_action( 'customize_register', 'theme_customize_register' );</pre>