how to create web services in PHP for XML and JSON data?

Web services are taking over the world. I credit Twitter's epic rise to the availability of a simple but rich API. Why not use the same model for your own sites? Here's how to create a basic web service that provides an XML or JSON response using some PHP and MySQL.

The PHP / MySQL

<?php
if(isset($_GET['user']) && intval($_GET['user'])) {
 $number_of_posts = isset($_GET['num']) ? intval($_GET['num']) : 10; //10 is the default
 $format = strtolower(@$_GET['format']) == 'json' ? 'json' : 'xml'; //xml is the default
  $user_id = intval($_GET['user']); //no default
$link = mysql_connect('localhost','root','') or die('Cannot connect to the DB');
mysql_select_db('webServices',$link) or die('Cannot select the DB');
/* grab the posts from the db */
  $query = "SELECT post_title, guid FROM wp_posts WHERE post_author = $user_id AND post_status = 'publish' ORDER BY ID DESC LIMIT $number_of_posts";
  $result = mysql_query($query,$link) or die('Errant query:  '.$query);
  /* create one master array of the records */
  $posts = array();
  if(mysql_num_rows($result)) {
    while($post = mysql_fetch_assoc($result)) {
      $posts[] = array('post'=>$post);
    }
  }
  
   if($format == 'json') {
    header('Content-type: application/json');
    echo json_encode(array('posts'=>$posts));
  }
  
   else {
    header('Content-type: text/xml');
    echo '<posts>';
    foreach($posts as $index => $post) {
      if(is_array($post)) {
        foreach($post as $key => $value) {
          echo '<',$key,'>';
          if(is_array($value)) {
            foreach($value as $tag => $val) {
              echo '<',$tag,'>',htmlentities($val),'</',$tag,'>';
            
            
            }
          }
          echo '</',$key,'>';
        }
      }
    }
    echo '</posts>';
  }

}
?>

With the number of persons hitting your web service (hopefully), you'll need to do adequate validation before attempting to connect to the database to avoid injection attacks. Once we get the desired results from the database, we cycle through the results to populate our return results array. Depending upon the response type desired, we output the proper header and content in the desired format.

Take the following sample URL for example:

http://mydomain.com/web-service.php?user=2&num=10&format=jsoneb-service.php?user=2&num=10

Now, we can take a look at the possible results of the URL.

The XML Output

c<posts>
  <post>
    <post_title>SSLmatic SSL Certificate Giveaway Winners</post_title>
    <guid>http://davidwalsh.name/?p=2304</guid>
  </post>
  <post>
    <post_title>MooTools FileManager</post_title>
    <guid>http://davidwalsh.name/?p=2288</guid>
  </post>
  <post>
    <post_title>PHPTVDB: Using PHP to Retrieve TV Show Information</post_title>
    <guid>http://davidwalsh.name/?p=2266</guid>
  </post>
  <post>
    <post_title>David Walsh: The Lost MooTools Plugins</post_title>
    <guid>http://davidwalsh.name/?p=2258</guid>
  </post>
  <post>
    <post_title>Create Short URLs Using U.Nu</post_title>
    <guid>http://davidwalsh.name/?p=2218</guid>
  </post>
  <post>
    <post_title>Create Bit.ly Short URLs Using PHP</post_title>
    <guid>http://davidwalsh.name/?p=2194</guid>
  </post>
  <post>
    <post_title>Represent Your Repositories Using the GitHub Badge!</post_title>
    <guid>http://davidwalsh.name/?p=2178</guid>
  </post>
  <post>
    <post_title>ZebraTable</post_title>
    <guid>http://davidwalsh.name/?page_id=2172</guid>
  </post>
  <post>
    <post_title>MooTools Zebra Table Plugin</post_title>
    <guid>http://davidwalsh.name/?p=2168</guid>
  </post>
  <post>
    <post_title>SSLmatic: Quality, Cheap SSL Certificates and Giveaway!</post_title>
    <guid>http://davidwalsh.name/?p=2158</guid>
  </post>
</posts>

Take this next sample URL for example:

cohttp://mydomain.com/web-service.php?user=2&num=10&format=json

Now, we can take a look at the possible results of the URL.

The JSON Output

{"posts":[{"post":{"post_title":"SSLmatic SSL Certificate Giveaway Winners","guid":"http:\/\/davidwalsh.name\/?p=2304"}},{"post":{"post_title":"MooTools FileManager","guid":"http:\/\/davidwalsh.name\/?p=2288"}},{"post":{"post_title":"PHPTVDB: Using PHP to Retrieve TV Show Information","guid":"http:\/\/davidwalsh.name\/?p=2266"}},{"post":{"post_title":"David Walsh: The Lost MooTools Plugins","guid":"http:\/\/davidwalsh.name\/?p=2258"}},{"post":{"post_title":"Create Short URLs Using U.Nu","guid":"http:\/\/davidwalsh.name\/?p=2218"}},{"post":{"post_title":"Create Bit.ly Short URLs Using PHP","guid":"http:\/\/davidwalsh.name\/?p=2194"}},{"post":{"post_title":"Represent Your Repositories Using the GitHub Badge!","guid":"http:\/\/davidwalsh.name\/?p=2178"}},{"post":{"post_title":"ZebraTable","guid":"http:\/\/davidwalsh.name\/?page_id=2172"}},{"post":{"post_title":"MooTools Zebra Table Plugin","guid":"http:\/\/davidwalsh.name\/?p=2168"}},{"post":{"post_title":"SSLmatic: Quality, Cheap SSL Certificates and Giveaway!","guid":"http:\/\/davidwalsh.name\/?p=2158"}}]}

Creating a basic web service is very simple and encourages your users to spread the word about your website or service. Want more traffic? Want your website to grow without you putting in all the effort? Create a web service!




 MYSQL data base Script:

-- phpMyAdmin SQL Dump

-- version 3.3.9

-- http://www.phpmyadmin.net

--

-- Host: localhost

-- Generation Time: Jul 21, 2011 at 01:44 PM

-- Server version: 5.5.8

-- PHP Version: 5.3.5

SET SQL_MODE="NO_AUTO_VALUE_ON_ZERO";

/*!40101 SET @OLD_CHARACTER_SET_CLIENT=@@CHARACTER_SET_CLIENT */;

/*!40101 SET @OLD_CHARACTER_SET_RESULTS=@@CHARACTER_SET_RESULTS */;

/*!40101 SET @OLD_COLLATION_CONNECTION=@@COLLATION_CONNECTION */;

/*!40101 SET NAMES utf8 */;

--

-- Database: `webservices`

--

CREATE DATABASE `webservices` DEFAULT CHARACTER SET latin1 COLLATE latin1_swedish_ci;

USE `webservices`;

-- --------------------------------------------------------

--

-- Table structure for table `wp_posts`

--

CREATE TABLE IF NOT EXISTS `wp_posts` (

  `id` int(11) NOT NULL AUTO_INCREMENT,

  `post_title` varchar(255) NOT NULL,

  `guid` varchar(255) NOT NULL,

  `post_author` varchar(255) NOT NULL,

  `post_status` varchar(255) NOT NULL,

  PRIMARY KEY (`id`)

) ENGINE=InnoDB  DEFAULT CHARSET=latin1 AUTO_INCREMENT=4 ;

--

-- Dumping data for table `wp_posts`

--

INSERT INTO `wp_posts` (`id`, `post_title`, `guid`, `post_author`, `post_status`) VALUES

(1, 'HeadFirst', 'hello', '2', 'publish'),

(2, 'cpp', '12345', '2', 'publish'),

(3, 'c', '12456', '2', 'publish');