How to do an internal search engine with the GET method?

I need you to please show me a simple example of an internal search engine. But seriously a very simple example, let's say minimalist, just to know the basic principles when building a search engine ... I'm trying it with the GET method, like google, but it does not work out ... before I was trying with java script but I do not think you can pick up the GET.

    <form action="" method="GET">
      <input type="text" name="sea" />
      <input type="submit" value="search" />
    </form>

    <?php
      if ( $_GET["name"] == "lalo" ) {
        echo '<a href="http://localhost/PHP%20Y%20SQL/practice/practica.php"></a>';
      }
?>

I clarify that I do not want to make the search engine with a database. I do not see it necessary. It is only to search internally. I also do not want to complicate myself. Questions: Is the super global GET indispensable, or can it be done without it? I suppose it is not necessary the computer security for this case that I want to make a search engine without a database, right?