Tag Archives: Plugin

How to use PHP’s namespaces and constants within your WordPress plugins

3 Replies

Recently I switched from using a class to emulate a namespace in my WordPress plugins to actually using PHP’s namespace, which is available in PHP 5.3.0 or greater. I’m going to demonstrate some things that all my plugins thus far have in common.

1. Create a namespace

Right before your plugin meta data comment, you must lead with your namespace (otherwise PHP will complain):

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namespace CompanyName\PluginName;
namespace CompanyName\PluginName;

I use a master namespace for everything I do (CompanyName) and a sub-namespace for the specific plugin I’m working on (PluginName).

2. Define a namespace constant

After the plugin meta data comment I define a constant, in other words, a shortcut to reference my namespace within WordPress hooks. It’s just less to type in the future and I can change my namespace without affecting plugin functionality.

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define(__NAMESPACE__ . '\NS', __NAMESPACE__ . '\\');
define(__NAMESPACE__ . '\NS', __NAMESPACE__ . '\\');

What this allows me to do is use a constant called NS to render CompanyName\PluginName\ so that after leading with NS in a WordPress hook callback, all I need to provide is my function name.

To create additional constants within your namespace, you can do that like so:

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define(NS . 'PS', 'plugin-slug');
define(NS . 'PS', 'plugin-slug');

3. Use your namespace constant in a WordPress hook

Here is what a function and a hook looks like in a namespaced environment:

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function initialize_plugin() {
 
}
 
add_action(
  'init',
  NS . 'initialize_plugin'
);
function initialize_plugin() {

}

add_action(
  'init',
  NS . 'initialize_plugin'
);

It’s really not that much different compared to not using a namespace and it certainly looks a lot cleaner than if you were using a class.

4. Use core WordPress functions

There are times where you need to use WordPress functions like the register_activation_hook, for example. It’s important to remember to change the namespace back to the global namespace for those functions.

The way to do that is to precede the function with a backslash:

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\register_activation_hook(__FILE__, NS . 'register_activation_hook');
\register_activation_hook(__FILE__, NS . 'register_activation_hook');

This should get you started and if you have any questions, leave them in the comments below.

-RS

$wpdb queries not working properly on child sites in WordPress multisite install

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I’m working on a WordPress multisite plugin that uses a global table to store logs. When a user performs a certain action on my site, I’m executing a function similar to this one:

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function add_log($source, $user_id, $action, $status) {
  global $wpdb, $blog_id;
  $table_name = $wpdb->prefix . LOG_TABLE;
  $IP = $_SERVER['REMOTE_ADDR'];
  $result = $wpdb->insert($table_name, 
    array(
      'source'  => $source,
      'site_id'   => $blog_id,
      'user_id' => $user_id,
      'action'  => $action,
      'status'  => $status,
      'IP'    => $IP
    ), 
    array(
      '%s',
      '%d', 
      '%d',
      '%s',
      '%s',
      '%s'
    ) 
  );
}
function add_log($source, $user_id, $action, $status) {
	global $wpdb, $blog_id;
	$table_name = $wpdb->prefix . LOG_TABLE;
	$IP = $_SERVER['REMOTE_ADDR'];
	$result = $wpdb->insert($table_name, 
		array(
			'source'	=> $source,
			'site_id' 	=> $blog_id,
			'user_id'	=> $user_id,
			'action'	=> $action,
			'status'	=> $status,
			'IP'		=> $IP
		), 
		array(
			'%s',
			'%d', 
			'%d',
			'%s',
			'%s',
			'%s'
		) 
	);
}

This works well on the base site (where blog_id = 1) of the WordPress multisite install, but for some reason it wasn’t capturing any logs on the other sites.

After some troubleshooting, which I did by modifying the function temporarily to this:

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function add_log($source, $user_id, $action, $status) {
  global $wpdb, $blog_id;
  define('DIEONDBERROR', true);
  $wpdb->show_errors();
  $table_name = $wpdb->prefix . LOG_TABLE;
  $IP = $_SERVER['REMOTE_ADDR'];
  $result = $wpdb->insert($table_name, 
    array(
      'source'    => $source,
      'site_id'   => $blog_id,
      'user_id' => $user_id,
      'action'    => $action,
      'status'    => $status,
      'IP'      => $IP
    ), 
    array(
      '%s',
      '%d', 
      '%d',
      '%s',
      '%s',
      '%s'
    ) 
  );
  $wpdb->print_error();
}
function add_log($source, $user_id, $action, $status) {
	global $wpdb, $blog_id;
	define('DIEONDBERROR', true);
	$wpdb->show_errors();
	$table_name = $wpdb->prefix . LOG_TABLE;
	$IP = $_SERVER['REMOTE_ADDR'];
	$result = $wpdb->insert($table_name, 
		array(
			'source'		=> $source,
			'site_id' 	=> $blog_id,
			'user_id'	=> $user_id,
			'action'		=> $action,
			'status'		=> $status,
			'IP'			=> $IP
		), 
		array(
			'%s',
			'%d', 
			'%d',
			'%s',
			'%s',
			'%s'
		) 
	);
	$wpdb->print_error();
}

I found out that $wpdb->prefix was not always wp_ as I expected, but it was wp_2_ or wp_3_, depending on the site the log was generated on. That actually makes a whole lot of sense.

The proper way to fix this is to indicate that you want the base prefix, not the individual site’s prefix.

The solution is to change $wpdb->prefix to $wpdb->base_prefix.

PS: If you are creating a plugin that will work on both single and multisite WordPress installs, it’s helpful to know that $wpdb->base_prefix is set on both of those versions, meaning you can always use it.

-RS

Passing in a “from” header to wp_mail() does not work

2 Replies

I ran into an issue today where I was setting the “from” header in wp_mail(), but it didn’t show up when I received the email. The code looks like this:

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$headers = 'From: Company <no-reply@company.com>' . "\r\n";
wp_mail($email, $subject, $message, $headers);
$headers = 'From: Company <no-reply@company.com>' . "\r\n";
wp_mail($email, $subject, $message, $headers);

I learned that the only reason my “from” header wouldn’t show up correctly is if one of the following filters overwrites it:

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add_filter('wp_mail_from','custom_wp_mail_from');
function custom_wp_mail_from($email) {
  return 'wordpress@company.com';
}
 
add_filter('wp_mail_from_name','custom_wp_mail_from_name');
function custom_wp_mail_from_name($name) {
  return 'WordPress';
}
add_filter('wp_mail_from','custom_wp_mail_from');
function custom_wp_mail_from($email) {
  return 'wordpress@company.com';
}

add_filter('wp_mail_from_name','custom_wp_mail_from_name');
function custom_wp_mail_from_name($name) {
  return 'WordPress';
}

Most likely you have plugin enabled that uses the previous filters to overwrite the “from” header that is being passed into wp_mail().

You have two options to fix the issue:

  1. You disable the plugin that’s causing this.
  2. You overwrite the plugin’s filter by creating another filter right before calling wp_mail().

It would be a good practice for you to remove that filter upon sending the email, especially if you are creating a plugin that’s going to be used by an audience other than yourself. The reason for this is now apparent :) .

You can do this via the remove_filter() function:

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remove_filter('wp_mail_from','custom_wp_mail_from');
remove_filter('wp_mail_from_name','custom_wp_mail_from_name');
remove_filter('wp_mail_from','custom_wp_mail_from');
remove_filter('wp_mail_from_name','custom_wp_mail_from_name');

Important: WordPress notes the following:

To remove a hook, the function and priority arguments must match when the hook was added. This goes for both filters and actions. No warning will be given on removal failure.

So if you set a priority, be sure to match it. In my example above, I didn’t specify a priority, so the default of 10 was used.

-RS