How do I style codes?

Question

How do I style a code ?
For example:
I posted this code on my blog:

<?= "Olá :D"; ?>

Only it will display normal, like a text, but inside the tag <pre></pre>.

But my question is, how do I stylize and make it visible to my readers like this:

And depending on the language, the stylization is different.
In my form I can select the type of code.. <pre><code class="language-php"><?= "Olá :D"; ?></code></pre>