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I have a plugin and I would like to be able to run the post content through some filters before it is saved to the database. From looking at the plugin api, I see that two hooks that look like they might be helpful:


The only problem is that it looks like save_post does not need return a variable, and so I don't know how to filter the content, and wp_insert_post looks documented.

I'd like to do something like this:


function my_function($post_content){
    return $post_content.' <br> This post was saved on '.time();

I am going to do something more useful than append a timestamp, namely running some regex filters, but this is the general type of filter / action I'm trying to add.


Please note that I want to intercept the data on it's way to being saved in the database - not when it is being displayed in the post (eg: Not by adding a filter to the_content)

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3 Answers 3

up vote 8 down vote accepted

The wp_insert_post_data filter can do that:

add_filter( 'wp_insert_post_data' , 'filter_post_data' , '99', 2 );

function filter_post_data( $data , $postarr ) {
    // Change post title
    $data['post_title'] .= '_suffix';
    return $data;
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got me going in the right direction, thanks. i think you actually need to use add_action though instead of add_filter. also your wpse35931_filter_post_data and filter_handler are incongruent... –  cwd Dec 9 '11 at 14:38

If you just want to add something similar at the end of all the posts, then I would suggest you use the the_content filter.

function append_to_content( $content ) {
    global $post;
    return $content.'<br />This post was saved on '.$post->post_date;
add_filter( 'the_content', 'append_to_content' );
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Thanks but I actually want to edit the data before it is saved in the database. –  cwd Dec 9 '11 at 14:25

Use filter content_save_pre exactly like the_content -- the difference is that it operates when a post is saved, rather than displayed.


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