API interface development with php

Why 80% of the code can not do farming architect? >>>  

For example: url interfaces file is: http: //url.com/api.php id = 001 interface file program: <php // get accepted by value $ id = $ _GET [ 'id']; // execution?? function api ($ id); // defined function function api ($ id) {// function body $ result = array (1,2,3); return $ result;}?>

Reproduced in: https: //my.oschina.net/itfanr/blog/195609