function one(){
echo "one";
}
function two(){
echo "two";
}
function three(){
echo "three";
}
function run_some_function(){
if(!isset($_REQUEST['function_name'])) return;
//Call it automatically for valid function names
call_user_func($_REQUEST['function_name']);
//or use if/select etc
if($_REQUEST['function_name'] == 'one') one();
}
[add_action](http://codex.wordpress.org/Function_Reference/add_action)( '[init](http://codex.wordpress.org/Plugin_API/Action_Reference/init)', 'run_some_function');