How Wordpress Displaying Shortcode In Post Content?

Here is the solution I come up with after 30 minutes researching:

function wpse_175564() {

  // The html goodies with shortcodes
       $htmlcodes = '<div class="akismet_activate">
                <div class="aa_a">A</div>
                <div onclick="document.akismet_activate.submit();" class="aa_button_container">

            [the_shortcode id="4"]

            <div class="aa_button_border">
                <div class="aa_button">Activate your Akismet account</div>
                </div>
                </div>
                <div class="aa_description"><strong>Almost done</strong>
     - [the_shortcode id="4"] activate your account and say goodbye to comment spam</div>
                </div>';
         // End of HTML Goodies

               // Let's get the shortcode inside the string and execute it!

                $pattern = get_shortcode_regex();
  if (preg_match_all( '/'. $pattern .'/s', $htmlcodes, $matches ) && array_key_exists( 2, $matches )) {

       foreach($matches[0] as $i => $v){
          $htmlcodes = preg_replace($v , do_shortcode($v), $htmlcodes);
          $htmlcodes =  str_replace(array('[',']'), '', $htmlcodes);
         }


  } 

 return $htmlcodes;

}

Not sure whether that's the best solution or not, but it works...!

If you want to insert a shortcode directly into the php template, you have to use do_shortcode().

For example:

<?php echo do_shortcode( '[the_shortcode id="4"]' ); ?>