I need some help with this small php search script,

I have a small HTML form...

<form action="search.php" method="post">
     <input type="text" name="search"><br>
     <input type="submit" value="Search">
</form>

What they will do is enter a username and what I am trying to get is information based on that username displayed in a table. For example, I enter Mike (which is a username) and then in the table it will display the country, city of the person (all this information is already in the database).

Thanks in advanced.