Using WordPress ‘pre_user_id’ PHP filter

The ‘pre_user_id’ filter allows you to modify the comment author’s user ID before it is set in WordPress. This can be useful in cases where you need to alter the user ID associated with a comment.

Usage

To use this filter, you need to add a custom function to your theme’s functions.php file or a custom plugin. Then, you’ll hook your function to the pre_user_id filter.

Code Example

function my_custom_pre_user_id( $user_id ) {
    // Your custom code here
    return $user_id;
}
add_filter( 'pre_user_id', 'my_custom_pre_user_id', 10, 1 );

Parameters

• $user_id (int): The comment author’s user ID.

Examples

Assign a default user ID to anonymous comments

function set_default_user_id( $user_id ) {
    if ( empty( $user_id ) ) {
        return 1; // Set the default user ID for anonymous comments
    }
    return $user_id;
}
add_filter( 'pre_user_id', 'set_default_user_id', 10, 1 );

In this example, if a comment is submitted without a user ID, it will be assigned the user ID “1”.

Swap user ID for a specific user

function swap_user_id( $user_id ) {
    if ( $user_id == 5 ) {
        return 10; // Swap user ID 5 with user ID 10
    }
    return $user_id;
}
add_filter( 'pre_user_id', 'swap_user_id', 10, 1 );

This code swaps the user ID of a comment author with user ID 5 to user ID 10.

Increment all user IDs by one

function increment_user_id( $user_id ) {
    return $user_id + 1; // Increment the user ID by 1
}
add_filter( 'pre_user_id', 'increment_user_id', 10, 1 );

This example increments all comment author user IDs by 1.

Assign a specific user ID for comments from a specific IP address

function assign_user_id_by_ip( $user_id ) {
    if ( $_SERVER['REMOTE_ADDR'] == '123.45.67.89' ) {
        return 99; // Set user ID to 99 for comments from the specific IP address
    }
    return $user_id;
}
add_filter( 'pre_user_id', 'assign_user_id_by_ip', 10, 1 );

This code sets the user ID of comments from a specific IP address (123.45.67.89) to 99.

Remove user ID for comments containing specific keywords

function remove_user_id_for_keywords( $user_id ) {
    $keywords = array( 'spam', 'fake' );
    $comment_content = $_POST['comment'];

    foreach ( $keywords as $keyword ) {
        if ( strpos( $comment_content, $keyword ) !== false ) {
            return 0; // Remove user ID if the comment contains specific keywords
        }
    }
    return $user_id;
}
add_filter( 'pre_user_id', 'remove_user_id_for_keywords', 10, 1 );

In this example, if a comment contains any of the specified keywords (‘spam’ or ‘fake’), the user ID will be removed (set to 0).