How to build a RESTful API?

Here is a very simply example in simple php.

There are 2 files client.php & api.php. I put both files on the same url : http://localhost:8888/, so you will have to change the link to your own url. (the file can be on two different servers).

This is just an example, it's very quick and dirty, plus it has been a long time since I've done php. But this is the idea of an api.

client.php

<?php

/*** this is the client ***/


if (isset($_GET["action"]) && isset($_GET["id"]) && $_GET["action"] == "get_user") // if the get parameter action is get_user and if the id is set, call the api to get the user information
{
  $user_info = file_get_contents('http://localhost:8888/api.php?action=get_user&id=' . $_GET["id"]);
  $user_info = json_decode($user_info, true);

  // THAT IS VERY QUICK AND DIRTY !!!!!
  ?>
    <table>
      <tr>
        <td>Name: </td><td> <?php echo $user_info["last_name"] ?></td>
      </tr>
      <tr>
        <td>First Name: </td><td> <?php echo $user_info["first_name"] ?></td>
      </tr>
      <tr>
        <td>Age: </td><td> <?php echo $user_info["age"] ?></td>
      </tr>
    </table>
    <a href="http://localhost:8888/client.php?action=get_userlist" alt="user list">Return to the user list</a>
  <?php
}
else // else take the user list
{
  $user_list = file_get_contents('http://localhost:8888/api.php?action=get_user_list');
  $user_list = json_decode($user_list, true);
  // THAT IS VERY QUICK AND DIRTY !!!!!
  ?>
    <ul>
    <?php foreach ($user_list as $user): ?>
      <li>
        <a href=<?php echo "http://localhost:8888/client.php?action=get_user&id=" . $user["id"]  ?> alt=<?php echo "user_" . $user_["id"] ?>><?php echo $user["name"] ?></a>
    </li>
    <?php endforeach; ?>
    </ul>
  <?php
}

?>

api.php

<?php

// This is the API to possibility show the user list, and show a specific user by action.

function get_user_by_id($id)
{
  $user_info = array();

  // make a call in db.
  switch ($id){
    case 1:
      $user_info = array("first_name" => "Marc", "last_name" => "Simon", "age" => 21); // let's say first_name, last_name, age
      break;
    case 2:
      $user_info = array("first_name" => "Frederic", "last_name" => "Zannetie", "age" => 24);
      break;
    case 3:
      $user_info = array("first_name" => "Laure", "last_name" => "Carbonnel", "age" => 45);
      break;
  }

  return $user_info;
}

function get_user_list()
{
  $user_list = array(array("id" => 1, "name" => "Simon"), array("id" => 2, "name" => "Zannetie"), array("id" => 3, "name" => "Carbonnel")); // call in db, here I make a list of 3 users.

  return $user_list;
}

$possible_url = array("get_user_list", "get_user");

$value = "An error has occurred";

if (isset($_GET["action"]) && in_array($_GET["action"], $possible_url))
{
  switch ($_GET["action"])
    {
      case "get_user_list":
        $value = get_user_list();
        break;
      case "get_user":
        if (isset($_GET["id"]))
          $value = get_user_by_id($_GET["id"]);
        else
          $value = "Missing argument";
        break;
    }
}

exit(json_encode($value));

?>

I didn't make any call to the database for this example, but normally that is what you should do. You should also replace the "file_get_contents" function by "curl".

In 2013, you should use something like Silex or Slim

Silex example:

require_once __DIR__.'/../vendor/autoload.php'; 

$app = new Silex\Application(); 

$app->get('/hello/{name}', function($name) use($app) { 
    return 'Hello '.$app->escape($name); 
}); 

$app->run(); 

Slim example:

$app = new \Slim\Slim();
$app->get('/hello/:name', function ($name) {
    echo "Hello, $name";
});
$app->run();