Is there a way to append the image id class to existing attached images in the post content automagically with a php function? That would be incredibly awesome.

Here is what I have so far. It seems like it should work, in theory. What am I doing wrong?

function be_attachment_id_on_images( $attr, $attachment ) {
    if( !strpos( $attr['class'], 'wp-image-' . $attachment->ID ) )
        $attr['class'] .= ' wp-image-' . $attachment->ID;
    return $attr;
}
add_filter( 'wp_get_attachment_image_attributes', 'be_attachment_id_on_images', 10, 2 );

if ( current_user_can( 'manage_options' ) && is_admin()){
function my_update_posts() {

        $args = array(
        'post_type' => 'post',
        'numberposts' => -1,
        'category' => 1,
        'ID' => 1,
    );

    $myposts = get_posts($args);
    foreach ($myposts as $mypost){
        $content = $mypost->post_content;
        apply_filters('be_attachment_id_on_images', $content);
        $mypost->post_content = $content;
        wp_update_post( $mypost );
    }

}

add_action( 'admin_init', 'my_update_posts' );

}

Is there a way to append the image id class to existing attached images in the post content automagically with a php function? That would be incredibly awesome.

Here is what I have so far. It seems like it should work, in theory. What am I doing wrong?

function be_attachment_id_on_images( $attr, $attachment ) {
    if( !strpos( $attr['class'], 'wp-image-' . $attachment->ID ) )
        $attr['class'] .= ' wp-image-' . $attachment->ID;
    return $attr;
}
add_filter( 'wp_get_attachment_image_attributes', 'be_attachment_id_on_images', 10, 2 );

if ( current_user_can( 'manage_options' ) && is_admin()){
function my_update_posts() {

        $args = array(
        'post_type' => 'post',
        'numberposts' => -1,
        'category' => 1,
        'ID' => 1,
    );

    $myposts = get_posts($args);
    foreach ($myposts as $mypost){
        $content = $mypost->post_content;
        apply_filters('be_attachment_id_on_images', $content);
        $mypost->post_content = $content;
        wp_update_post( $mypost );
    }

}

add_action( 'admin_init', 'my_update_posts' );

}

• images

• Did you find a working solution for this? I'm running into the same issue after importing some posts from another platform into WordPress. – Mark B Commented Aug 12, 2021 at 17:56

2 Answers 2

Shamelessly copied from here: https://letswp.io/add-attachment-id-to-the-class-of-wordpress-images/

add_filter( 'wp_get_attachment_image_attributes', 'add_image_id_class', 10, 2 );


function add_image_id_class( $attr, $attachment ) {

    $class_attr = isset( $attr['class'] ) ? $attr['class'] : '';

    $has_class = preg_match( '/wpimage\_[0-9]+/', $class_attr, $matches );


    if ( !$has_class ) {

        $class_attr .= sprintf( ' wpimage_%d', $attachment->ID );

        $attr['class'] = ltrim( $class_attr );

    }

    return $attr;

}

This add a class like wpimage_{ATTACHMENT_ID} for example wpimage_22.

According to this earlier answer, the wp_get_attachment_image_attributes filter only works for the Featured Image/Post Thumbnail, although I'm not sure if the assertion is correct. Other places claim it doesn't work with the block editor. You might try the get_image_tag_class() filter. Or, depending on your goals, it might suffice to use a slightly different approach: add a class to the body (using the body_class() filter), then use a css selector like body.special img (that doesn't give the ID, though).