Turn any PHP file into an API

api_call.js

var http = false;

if(navigator.appName = "Microsoft Internet Explorer"){
  http = new ActiveXObject("Microsoft.XMLHTTP");
} else {
  http = new XMLHttpRequest();
}

function doSomething(some_param){
  http.abort();
  http.open("POST","path/to/functions_and_api.php?action=someFunction&params="+some_param);
  http.onreadystatechange=function(){
    if(http.readyState == 4) {
      if(http.responseText){
        alert(http.responseText);
      }
    }
  }
  http.send(null);
}

/* call doSomething(some_params) to use your new "API" */

functions_and_api.php

<?php
/**
* This snippet of code allows you to turn any php file into one that
* responds to REQUESTS - unveiling all of the functions to web calls
* in the style of an API.
*
* The code as it exists here has gaping security issues. At the very
* simplest you should have an array of allowed function names that is
* checked before executing. I have a more secure version somewhere ...
*/

if($_REQUEST['action'] && $_REQUEST['params']){
  $function = $_REQUEST['action'];
  if(function_exists($function)){
    if($function($_REQUEST['params'])){
      echo "Successful {$function}";
    else{
      echo "Error running function - {$function}";
    }
  }else{
    echo "Unsuccessful call - attempted to run non-existant function";
  }
}
?>