WordPress has great filter support for getting at all sorts of specific bits of content and modifying it before output. Like the_content filter, which lets you access the markup for a post before it's output to the screen.
I'm trying to find a catch-all filter that gives me one last crack at modifying the final markup in its entirety before output.
I've browsed the list of filters a number of times, but nothing jumps out at me:
https://codex.wordpress.org/Plugin_API/Filter_Reference
Anyone know of one?
WordPress doesn't have a "final output" filter, but you can hack together one. The below example resides within a "Must Use" plugin I've created for a project.
Note: I haven't tested with any plugins that might make use of the "shutdown" action.
The plugin works by iterating through all the open buffer levels, closing them and capturing their output. It then fires off the "final_output" filter, echoing the filtered content.
Sadly, WordPress performs almost the exact same process (closing the open buffers), but doesn't actually capture the buffer for filtering (just flushes it), so additional "shutdown" actions won't have access to it. Because of this, the below action is prioritized above WordPress's.
wp-content/mu-plugins/buffer.php
<?php
/**
* Output Buffering
*
* Buffers the entire WP process, capturing the final output for manipulation.
*/
ob_start();
add_action('shutdown', function() {
$final = '';
// We'll need to get the number of ob levels we're in, so that we can iterate over each, collecting
// that buffer's output into the final output.
$levels = ob_get_level();
for ($i = 0; $i < $levels; $i++) {
$final .= ob_get_clean();
}
// Apply any filters to the final output
echo apply_filters('final_output', $final);
}, 0);
An example of hooking into the final_output filter:
<?php
add_filter('final_output', function($output) {
return str_replace('foo', 'bar', $output);
});
Edit:
This code uses anonymous functions, which are only supported in PHP 5.3 or newer. If you're running a website using PHP 5.2 or older, you're doing yourself a disservice. PHP 5.2 was released in 2006, and even though Wordpress (edit: in WP version < 5.2) STILL supports it, you should not use it.
The question is may be old, but I have found a better way to do it:
function callback($buffer) {
// modify buffer here, and then return the updated code
return $buffer;
}
function buffer_start() { ob_start("callback"); }
function buffer_end() { ob_end_flush(); }
add_action('wp_head', 'buffer_start');
add_action('wp_footer', 'buffer_end');
Explanation
This plugin code registers two actions – buffer_start and buffer_end.
buffer_start is executed at the end of the header section of the html. The parameter, the callback function, is called at the end of the output buffering. This occurs at the footer of the page, when the second registered action, buffer_end, executes.
The callback function is where you add your code to change the value of the output (the $buffer variable). Then you simply return the modified code and the page will be displayed.
Notes
Be sure to use unique function names for buffer_start, buffer_end, and callback, so they do not conflict with other functions you may have in plugins.
AFAIK, there is no hook for this, since the themes uses HTML which won't be processed by WordPress.
You could, however, use output buffering to catch the final HTML:
<?php
// example from php.net
function callback($buffer) {
// replace all the apples with oranges
return (str_replace("apples", "oranges", $buffer));
}
ob_start("callback");
?>
<html><body>
<p>It's like comparing apples to oranges.</p>
</body></html>
<?php ob_end_flush(); ?>
/* output:
<html><body>
<p>It's like comparing oranges to oranges.</p>
</body></html>
*/
#jacer, if you use the following hooks, the header.php also gets included.
function callback($buffer) {
$buffer = str_replace('replacing','width',$buffer);
return $buffer;
}
function buffer_start() { ob_start("callback"); }
function buffer_end() { ob_end_flush(); }
add_action('after_setup_theme', 'buffer_start');
add_action('shutdown', 'buffer_end');
I was using the top solution of this post (by kfriend) for a while. It uses an mu-plugin to buffer the whole output.
But this solution breaks the caching of wp-super-cache and no supercache-files are generated when i upload the mu-plugin.
So: If you are using wp-super-cache, you can use the filter of this plugin like this:
add_filter('wp_cache_ob_callback_filter', function($buffer) {
$buffer = str_replace('foo', 'bar', $buffer);
return $buffer;
});
Modified https://stackoverflow.com/users/419673/kfriend answer.
All code will be on functions.php. You can do whatever you want with the html on the "final_output" filter.
On your theme's 'functions.php'
//we use 'init' action to use ob_start()
add_action( 'init', 'process_post' );
function process_post() {
ob_start();
}
add_action('shutdown', function() {
$final = '';
// We'll need to get the number of ob levels we're in, so that we can iterate over each, collecting
// that buffer's output into the final output.
$levels = ob_get_level();
for ($i = 0; $i < $levels; $i++) {
$final .= ob_get_clean();
}
// Apply any filters to the final output
echo apply_filters('final_output', $final);
}, 0);
add_filter('final_output', function($output) {
//this is where changes should be made
return str_replace('foo', 'bar', $output);
});
You might try looking in the wp-includes/formatting.php file. For example, the wpautop function.
If you are looking for doing something with the entire page, look at the Super Cache plugin. That writes the final web page to a file for caching. Seeing how that plug-in works may give you some ideas.
Indeed there was a discusussion recently on the WP-Hackers mailing list about the topic of full page modification and it seems the consensus was that output buffering with ob_start() etc was the only real solution. There was also some discussion about the upsides and downsides of it: http://groups.google.com/group/wp-hackers/browse_thread/thread/e1a6f4b29169209a#
To summarize: It works and is the best solution when necessary (like in the WP-Supercache plugin) but slows down overall speeds because your content isn't allowed to be sent to the browser as its ready, but instead has to wait for the full document to be rendered (for ob_end() ) before it can be processed by you and sent to the browser.
To simplify previous answers, just use this in functions.php:
ob_start();
add_action('shutdown', function () {
$html = ob_get_clean();
// ... modify $html here
echo $html;
}, 0);
I've been testing the answers here now for a while, and since the cache breaking thing is still an issue, I came up with a slightly different solution. In my tests no page cache broke. This solution has been implemented into my WordPress plugin OMGF (which has 50k+ users right now) and no issues with page cache breaking has been reported.
First, we start an output buffer on template redirect:
add_action('template_redirect', 'maybe_buffer_output', 3);
function maybe_buffer_output()
{
/**
* You can run all sorts of checks here, (e.g. if (is_admin()) if you don't want the buffer to start in certain situations.
*/
ob_start('return_buffer');
}
Then, we apply our own filter to the HTML.
function return_buffer($html)
{
if (!$html) {
return $html;
}
return apply_filters('buffer_output', $html);
}
And then we can hook into the output by adding a filter:
add_filter('buffer_output', 'parse_output');
function parse_output($html)
{
// Do what you want. Just don't forget to return the $html.
return $html;
}
Hope it helps anyone.
I have run into problems with this code, as I end up with what seems to be the original source for the page so that some plugins has no effect on the page. I am trying to solve this now - I haven't found much info regarding best practises for collecting the output from WordPress.
Update and solution:
The code from KFRIEND didnt work for me as this captures unprocessed source from WordPress, not the same output that ends up in the browser in fact. My solution is probably not elegant using a globals variable to buffer up the contents - but at least I know get the same collected HTML as is delivered to the browser. Could be that different setups of plugins creates problems but thanks to code example by Jacer Omri above I ended up with this.
This code is in my case located typically in functions.php in theme folder.
$GLOBALS['oldschool_buffer_variable'] = '';
function sc_callback($data){
$GLOBALS['final_html'] .= $data;
return $data;
}
function sc_buffer_start(){
ob_start('sc_callback');
}
function sc_buffer_end(){
// Nothing makes a difference in my setup here, ob_get_flush() ob_end_clean() or whatever
// function I try - nothing happens they all result in empty string. Strange since the
// different functions supposedly have very different behaviours. Im guessing there are
// buffering all over the place from different plugins and such - which makes it so
// unpredictable. But that's why we can do it old school :D
ob_end_flush();
// Your final HTML is here, Yeeha!
$output = $GLOBALS['oldschool_buffer_variable'];
}
add_action('wp_loaded', 'sc_buffer_start');
add_action('shutdown', 'sc_buffer_end');
If you want to modify the output, you can use template_include:
add_filter( 'template_include', static function ( $template ) {
if ( basename( $template ) === 'foo-template.php' ) {
echo str_replace( 'foo', 'bar', file_get_contents( $template ) );
}
return null;
} );
If instead you want to override the output completely, you can use the action template_redirect.
add_action( 'template_redirect', static function () {
wp_head();
echo 'My output.';
wp_footer();
exit;
} );
I would like to know how to run a function when a meta information of a custom post type is changed.
For example, I have a radio box associated with a custom post type. And made it with metaboxes, and when I change the option, I would like to run a function.
How would I do that?
Originally in OP's question.
I think I found what I wanted
function do_my_stuff($post_ID) {
//do my stuff here;
return $post_ID;
}
add_action('save_post', 'do_my_stuff');
Wordpress: executing function when saving or editing post
But is it possible to track what changes were made?
Yup, did it with your help diggy, but had to change something.
function do_my_stuff($post_ID) {
$newvalue = $_POST['my_metabox_value'];
echo $newvalue;
$oldvalue= get_post_meta($post_id, 'my_metabox_value', true );
echo $oldvalue;
}
add_action('pre_post_update', 'do_my_stuff');
Good morning,
I need a hook or something to call to separate new posts from updated ones.
I want to execute some code only for new posts... something like that:
add_action('publish_post', myfunction);
function myfunction( $post_id ){
if <new post> {
/* do something */
}
else {
/* do nothing */
}
}
I'm using WP v3.5
Any suggestion?
First, you want to use the draft_to_publish hook:
add_action('draft_to_published', 'my_function');
However, this can fire multiple times if a post is published, unpublished, and then published again. To ensure that your action only fires one time, set a custom meta element for the post at the end of your function. At the start of your function, check if you meta element is set and skip the action if it is.
--- Added ---
Here is a sample on how the repeat action protection would work (untested code - so might need a little work):
function my_function() {
$already_done = get_post_meta($post_id, 'do_once', true);
if(!$already_done) {
// Do what you need to do here
add_post_meta($post_id, 'do_once', 1, true);
}
}
I am using the save_post action to inspect a metadata field in a custom post and take some action on that value. This is the essential guts of how I am doing it:
add_action('save_post', 'my_save_post');
function my_save_post($post_id)
{
// Check if not autosaving, processing correct post type etc.
// ...
// Get the custom field value.
$my_field_value = get_post_meta($post_id, 'my_field', true);
// Do some action
// ...
}
This works fine when updating the post through the admin page. However, when first creating the post, the my_field_value is always empty. The field does get saved correctly, but this action trigger does not seem to be able to see it, nor any other custom field values.
I would like the action to be performed on all posts of this type created, and I will be importing many through the CSV Imported plugin. Even then, the custom fields do get imported correctly, and the action trigger does get fired for each row imported, but the save_post action still cannot see the custom field value.
So far as I can see from documentation, the post has already been created by the time this action fires, so I should always be able to see that custom metafield.
The answer, it seems, is in the order in which things happen. When creating a post from a form, the custom fields are all collected by the appropriate actions and added to the post before my save_post action fires. This means my trigger is able to see those custom field values.
When importing from CSV, the basic post is created first, and then the custom metafields are added. The save_post trigger fires on the first creation, before the metafields are added, and so the custom field data is not visible to the save_post action.
My solution was to catch the updates of the metadata using the updated_post_meta and added_post_meta actions as well as the save_post action:
add_action('updated_post_meta', 'my_updated_post_meta', 10, 4);
add_action('added_post_meta', 'my_updated_post_meta', 10, 4);
function my_updated_post_meta($meta_id, $post_id, $meta_key, $meta_value)
{
// Make sure we are handling just the meta field we are interested in.
if ($meta_key != 'my_custom_field') return;
if (wp_is_post_revision($post_id)) return;
if (get_post_type($post_id) != 'my_post_type') return;
if (trim($meta_value) == '') return;
// Do my custom task (linking this post to a parent post in a different
// post type). This is the same task performed by the save_post action.
my_link_product_track($post_id, trim($meta_value));
}
That is essentially what I do, and it seems to work well. I do encapsulate all the above into a custom class in the theme, and don't recommend using global scope variables as shown here, but this is just to show the method.
You should look at using $post->ID instead of $post_id -
$my_field_value = get_post_meta($post->ID, 'my_field', true);
get_post_meta in the Codex
EDIT:
Could you do something like this?
if($post->ID == ''){
$pid = $post_id;
} else {
$pid = $post->ID;
}
//$pid = $post->ID or $post_id, whichever contains a value
$my_field_value = get_post_meta($pid, 'my_field', true);
something that looks for a value in $post->ID and $post_id, and uses whichever one isn't blank?
I am using developing a child theme for Woothemes' Canvas.
I am trying to use functions.php in the child theme to only use actions on my custom post type.
This code doesn't seem to be working:
add_action( 'woo_post_inside_after', 'my_geo_mashup' );
function my_geo_mashup() {
echo GeoMashup::map();
if ($post->post_type == 'listings') {
//My function
}
}
add_action( 'woo_post_inside_before', 'listings_nivo' );
function listings_nivo() {
echo do_shortcode('[nivo source="current-post" ]');
if ($post->post_type == 'listings') {
//My function
}
}
So, I'm unsure how to get the above to work properly and only show these items on the custom post type, or only for the custom post type template single-listings.php (as I only want the map and slider to show on the actual post, not on the blog page (archive.php)
Rather than making the entire $post object global, you can just make $post_type global instead. Ex below.
I'm not exactly sure where that function is being loaded, but make sure you hook somewhere within the post. If the action is before, as far as I know and from experience, the post variable will be null.
Just as a test, try running the action in wp_footer Ex. add_action( 'wp_footer', 'listings_nivo' );
See if that yeilds any results.
if echoing var_dump($post) is still null, well, not sure where to go from there.
So you can try running the below, then run the action in the appropriate place if it works:
function listings_nivo() {
echo do_shortcode('[nivo source="current-post" ]');
global $post_type;
// Diagnostic purposes
echo var_dump($post_type);
if ($post_type == 'listings') {
//My function
}
}
add_action( 'wp_footer', 'listings_nivo' );
Check your error log or turn wp_debug to true in your wp-config.php file if nothing else to see if anything else is going on.
Best of luck!
Inside your function, try adding global $post;. Then to see what you are getting with $post->post_type echo it out to the screen. As long as this gives you "listings", your code should work. If not, there's probably another issue at play.