Posting Data to REST API using JSON and PHP - php

Question

I've been looking around at similar topics on REST APIs but I am still having some confusion in my project, mostly with the PHP side of things.
USPS provides a REST API with functions that can be called via URL like this: https://epfws.usps.gov/ws/resources/epf/login
To make any call successfully, I have been told that a JSON object must be created and passed as a "POST parameter" with the expected values.
This is the JSON object that needs to be passed in this case:
obj=
{
"login":"loginExample",
"pword":"passwordExample"
}
I have also been given a PHP class that is supposed to manage these calls. This is the login function:
public function login ()
{
// Set up the parameters for a login attempt
$jsonData = array(
'login' => $this->loginUser,
'pword' => $this->loginPass,
);
// Make a login request
$jsonResponse = $this->pullResource
('/epf/login', 'POST', $jsonData);
return $jsonResponse;
}
So I have a few questions regarding this:
The document they sent says
"To make the request calls, a JSON object will need to be created and passed as a POST form parameter obj={jsonObject} for security reasons using content-type “application/x-www-form-urlencoded”."
I know that the login function contains the correct input values that USPS' REST API is wanting, but I'm not sure how to pass them as "obj", or how to apply the "content-type".
I have a "constant" defined at the top of my PHP script that looks like this:
const EPF_BASE_URL = 'https://epfws.usps.gov/ws/resources';
And I noticed in the actual functions that this part of the link is left out and they simply reference '/epf/login' as you can see above. Since "$this" contains lots of different values I'm wondering how it supposedly finds EPF_BASE_URL as needed. Is it similar to how 'using' directives work in C#?
What is the easiest way to call this function and display the result? This is my biggest question. Would I use a separate PHP class with an HTML form? I understand the concept of what it should do but I'm completely lost setting up a development environment for it.
I've been trying all of this with MAMP but would love to know if I'm on the right track or not.

Answer 1

That really depends on their API. Hopefully you get a string back that can be decoded to a JSON object (http://au.php.net/manual/en/function.json-decode.php). Some API might give a simple string that says 'SUCCESS' or 'FAIL'. You've got the code, so take a look at what $this->pullResponse() gives you.
If you've been given a PHP class that is supposed to support the API (hopefully from USPS), then it should already take care of putting the data in the form content, and ensuring is it submitted with the appropriate content-type.
A PHP const is more like a C# static string. It is very likely that the library will use the constant to create the end URL (i.e. EPF_BASE_URL . $resource). If you needed to run against a sand box environment, you could change that constant without having to change all the other code.
That's a very big question, because it depends on how you are programming your application. Procedural, MVC, existing frameworks, etc.
At the very least, you would set the loginUser and loginPass on the instantiated object, and call the login method`. You could then inspect the results, assuming the result is a JSON object, or use your favourite debugging method to see the contents.
I'm having a guess as the USPS API class name.
$uspsApi = new UspsApi();
$uspsApi->loginUser = 'username';
$uspsApi->loginPass = 'password';
$result = $uspsApi->login();
echo print_r($result, true);