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Third-Party Web APIs

  1. Overview
    1. A Web Application Programming Interface or Web API is a service that a client program can interface with using HTTP
    2. A third-party web API is a service provided by a third party, which is often free but requires registering for a key to access it
    3. Many third-party web APIs provides access to a large data set
    4. Some popular web APIs:
      1. Flickr API (photos)
      2. Bing Search API (web search)
      3. Facebook Graph API (Facebook social graph)
      4. Yahoo Fantasy Sports API
    5. Most third-party web APIs are RESTful, meaning they use a query string or path or access the API and return the results in XML or JSON
    6. Some web APIs are SOAP-based, which is more complicated and heavily dependent on transfering XML between the client and server
  2. General architecture
    1. Client-side usage (with CORS, JSONP, or proxy server) 
                 API Req
1) Browser ---------> Service Provider 

           XML/JSON
2) Browser <--------- Service Provider
    2. Server-side usage 
                 Request
1) Browser ---------> Web Server 

                                 API Req
2) Browser            Web Server ---------> Service Provider 

                                 XML/JSON
3) Browser            Web Server <--------- Service Provider 

           Response
4) Browser <--------- Web Server            Service Provider
  3. OMDb API
    1. OMDb API is a free web API to obtain movie information
    2. The movie data is obtained from IMDb
    3. You must obtain a free API key to use the service
    4. Example queries
      1. Example 1 - Search for all movies with the word "star" in the title

        http://www.omdbapi.com/?s=star&type=movie&apikey=APIKEY 

        {
  "Search": [
    {
      "Title": "Star Wars: Episode IV - A New Hope",
      "Year": "1977",
      "imdbID": "tt0076759",
      "Type": "movie"
    },
    {
      "Title": "Star Wars: Episode V - The Empire Strikes Back",
      "Year": "1980",
      "imdbID": "tt0080684",
      "Type": "movie"
    },
    etc...
    {
      "Title": "Star Trek II: The Wrath of Khan",
      "Year": "1982",
      "imdbID": "tt0084726",
      "Type": "movie"
    }
  ]
}
      2. Example 2 - Get info for movie with IMDB ID tt0076759 (returns JSON)

        http://www.omdbapi.com/?i=tt0076759&apikey=APIKEY 

        {  
   "Title":"Star Wars: Episode IV - A New Hope",
   "Year":"1977",
   "Rated":"PG",
   "Released":"25 May 1977",
   "Runtime":"121 min",
   "Genre":"Action, Adventure, Fantasy",
   "Director":"George Lucas",
   "Writer":"George Lucas",
   "Actors":"Mark Hamill, Harrison Ford, Carrie Fisher, Peter Cushing",
   "Plot":"Luke Skywalker joins forces with a Jedi Knight, a cocky pilot, a Wookiee, and two droids to save the galaxy from the Empire's world-destroying battle-station, while also attempting to rescue Princess Leia from the evil Darth Vader.",
   "Language":"English",
   "Country":"USA",
   "Awards":"Won 6 Oscars. Another 50 wins & 28 nominations.",
   "Poster":"https://images-na.ssl-images-amazon.com/images/M/MV5BZDk2NmNhZDgtZDgzZS00NTRkLWFiYjUtNGMzZTYwNTFhYjFmXkEyXkFqcGdeQXVyNzkwMjQ5NzM@._V1_SX300.jpg",
   "Ratings":[  
      {  
         "Source":"Internet Movie Database",
         "Value":"8.7/10"
      },
      {  
         "Source":"Rotten Tomatoes",
         "Value":"93%"
      },
      {  
         "Source":"Metacritic",
         "Value":"92/100"
      }
   ],
   "Metascore":"92",
   "imdbRating":"8.7",
   "imdbVotes":"1,009,663",
   "imdbID":"tt0076759",
   "Type":"movie",
   "DVD":"21 Sep 2004",
   "BoxOffice":"N/A",
   "Production":"20th Century Fox",
   "Website":"http://www.starwars.com/episode-iv/",
   "Response":"True"
}
  4. Accessing the movie API in JavaScript
    1. Use XMLHttpRequest to make GET request
    2. Set responseType to "json" if results are JSON-encoded
    3. Use encodeURIComponent() to ensure string used in HTTP request is URL-encoded
    4. Example 
      var search = "star wars";
var xhr = new XMLHttpRequest();
xhr.addEventListener("load", responseReceived);
xhr.responseType = "json";
xhr.open("GET", "https://www.omdbapi.com/?s=" + encodeURIComponent(search) + "&type=movie&apikey=APIKEY"); 
xhr.send();

function responseReceived() {
	// Display all movie titles
	if (this.response.Error) {
		console.log("Movie not found");
	} 
	else {
		var movies = this.response.Search;
		for (var i = 0; i < movies.length; i++) {
			console.log(movies[i].Title);
		}
	}
}
  5. Accessing a movie API in PHP
    1. Use file_get_contents($url) to make an HTTP request to the web API and get back the HTTP response body 
      $search = urlencode("star wars");   // URL-encode the string
$apikey = "APIKEY";

// Make HTTP request and wait for the response
$response = file_get_contents("http://www.omdbapi.com/?s=$search&y=&plot=short&r=json&apikey=$apikey");

if ($response === FALSE)
    die("Error contacting the web API");
else
{
	// Display JSON results
	echo "<pre>$response</pre>";
}
    2. Use json_decode($json) to parse the JSON and get back an object with a Search property that is an array of objects containing the movie data 
      // Parse JSON results
$obj = json_decode($response);
print_r($obj);
      Output: 
      (
    [Search] => Array
        (
            [0] => stdClass Object
                (
                    [Title] => Star Wars: Episode IV - A New Hope
                    [Year] => 1977
                    [imdbID] => tt0076759
                    [Type] => movie
                )
            [1] => stdClass Object
                (
                    [Title] => Star Wars: Episode V - The Empire Strikes Back
                    [Year] => 1980
                    [imdbID] => tt0080684
                    [Type] => movie
                )
            etc...
        )
)
    3. Example outputting the first movie title 
      echo "First title = " . $obj->Search[0]->Title;
      Output: 
      First title = Star Wars: Episode IV - A New Hope
    4. Example displaying the title of each movie 
      // Get the array of objects containing movie data
$search_results = $obj->Search;

// Loop through every movie
foreach ($search_results as $movie)
{
	echo "<p>Title: $movie->Title</p>\n";
}