Call PHP function from url?

Question

If I want to execute a php script, i just point the browser to www.something.com/myscript.php

But if i want to execute a specific function inside

Answer 1

 if (isset($GET[param_name])){

  if($GET[param_name] === value)
   {
      function 1... 
    } else if 
 {

function 2...
 }

}