So, I thought I would detail how to do that in WordPress in a plugin.

The plugin just has a basic options page (Settings -> Ajax4WP) and lets you save an option to the database via ajax. Go ahead and download and install it; you’ll see how simple it is.

1. Create a php file that will have our javascript code, and save it into your plugins folder.

The reason we need our javascript code to be in a PHP file is to get the “get_option(‘siteurl’)” value dynamically, since we’ll need that to reference our PHP file with the ajax function.

js-Ajax4WP.php (download the plugin files)

<?php
include('../../../wp-config.php');
$site_url = get_option('siteurl');
?>
jQuery(document).ready(function() {

   //when the link with the id of save_settings is clicked, get the value of the text field and start doing the ajax stuff
   jQuery('#save_settings').click(function() {

      var Ajax4WP_test_setting = jQuery("#Ajax4WP_test_setting").val();

      //action is the name of the php function in your main plugin file
      jQuery.post("<?php echo $site_url; ?>/wp-admin/admin-ajax.php", {action:"Ajax4WP_save_settings", 'cookie': encodeURIComponent(document.cookie), Ajax4WP_test_setting:Ajax4WP_test_setting},
      function(res)
      {
         var message_result = eval('(' + res + ')');
         if (!message_result.success) {
            jQuery("#Ajax4WP_test_setting").css("border","2px solid #cc0000");
         }
         alert(message_result.message + ' ' + message_result.setting);
      });

      return false;
   });

});

This is jQuery ajax code that takes the value of a text field and passes it to Ajax4WP_save_settings() in our plugin file. We use jQuery.post to define a post variable (Ajax4WP_test_setting) that PHP can use.

Once the plugin code does its thing on the server (step 2 below), it returns the result back to this function at “function(res)”. Then we eval the json result and use an alert to display a message.

2. Create your standard plugin file and put in the Ajax4WP_save_settings function.

Ajax4WP.php (download the plugin files)

...

// our ajax action:
add_action('wp_ajax_Ajax4WP_save_settings', array(&$this, 'Ajax4WP_save_settings'), 10);

function Ajax4WP_save_settings()
		{
		   $name = 'Ajax4WP_test_setting';
			$value = $_POST['Ajax4WP_test_setting'];

			if ($value == "") {
				$message_result = array(
					'setting' => "",
					'message' => 'Please enter a Setting Value!',
					'success' => FALSE
	         );
			}
			else {
			   update_option($name, $value);
				$message_result = array(
					'setting' => $value,
					'message' => 'Saved! You entered:',
				   'success' => TRUE
	         );
			}
			echo json_encode($message_result);
			exit;
		}
...

This is standard PHP to process a POST request. When we’re through, we echo the json_encode() result. NOTE: json_encode is a PHP >= 5.2 only function, so be sure you are up to date on your PHP install.

3. Make a php file that will contain basic html and will get included on our settings page

Ajax4WP-settings.php (download the plugin files)

<div id="Ajax4WP Settings" class="inside" style="margin-left: 29px; width: 200px;">

   <h3>Ajax4WP Settings</h3>

   <div id="loading_message"></div>

   <p>
   <label for="Ajax4WP_test_setting">Setting Value:</label>
   <br />
   <input type="text" id="Ajax4WP_test_setting" name="Ajax4WP_test_setting" value="<?php if (isset($this->Ajax4WP_test_setting)) { echo $this->Ajax4WP_test_setting; } ?>" size="20" />
   </p>

   <p><a href="#" id="save_settings" class="button button-highlighted">Save Settings</a></p>

</div>

This is just a “stub” and gets included in our plugin. That way we don’t have a lot of html code mucking up the main plugin file. You can see what’s going on better in the source code when you download the files.

I hope that helps you out if you are wondering how to use jQuery and ajax in your WordPress plugins. Please leave a comment if you have any questions. Thanks!