为特色图片添加用户元

Question

I'm developing a site in which a user is able to capture his/her pic(via .getusermedia) which updated as the post thumbnail.

The problem is that the post thumbnail gets updated for all users - I want the post thumbnail to be updated only for that particular user

function Generate_Featured_Image( $filename, $parent_post_id  ){
    require('/wp-load.php');

    $filetype = wp_check_filetype( basename( $filename ), null );

    $wp_upload_dir = wp_upload_dir();

    $attachment = array(
        'guid'           => $wp_upload_dir['url'] . '/' . basename(  $filename ), 
        'post_mime_type' => $filetype['type'],
        'post_title'     => preg_replace( '/\.[^.]+$/', '', basename(     $filename ) ),
        'post_content'   => '',
        'post_status'    => 'inherit'
    );

    $attach_id = wp_insert_attachment( $attachment, $filename,  $parent_post_id );

    require_once( ABSPATH . 'wp-admin/includes/image.php' );

    $attach_data = wp_generate_attachment_metadata( $attach_id, $filename );
    wp_update_attachment_metadata( $attach_id, $attach_data );

    //add_user_meta( $current_user_id, $parent_post_id, $attach_id);
    set_post_thumbnail( $parent_post_id, $attach_id );
}

script.php

Generate_Featured_Image( $addroot.$current_user_id.$extimage, 88  );
// addroot=path ext-extension(.jpg) (this is name of file saved)

i tried to user add_user_meta to accomplish the task but couldn't even get a start

UPDATE

<?php 
// $filename is succesfully saved as currentuserid+.jpg.
 $addroot = '/wp-content/uploads/2016/09/';


  $current_user_id = get_current_user_id();


$extimage = '.jpg';


$filename = $addroot.$current_user_id.$extimage;

 $filetype = wp_check_filetype( basename( $filename ), null );

 // Get the path to the upload directory.
 $wp_upload_dir = wp_upload_dir();

 // Prepare an array of post data for the attachment.
 $attachment = array(
'guid'           => $wp_upload_dir['url'] . '/' . basename( $filename ), 
'post_mime_type' => $filetype['type'],
'post_title'     => preg_replace( '/\.[^.]+$/', '', basename( $filename ) ),
'post_content'   => '',
'post_status'    => 'inherit'
  );

// Insert the attachment.
 $attach_id = wp_insert_attachment( $attachment, $filename, 0 );

 require_once( ABSPATH . 'wp-admin/includes/image.php' );

  // Generate the metadata for the attachment, and update the database record.
  $attach_data = wp_generate_attachment_metadata( $attach_id, $filename );
      wp_update_attachment_metadata( $attach_id, $attach_data );
     update_user_meta( get_the_ID(), $filename , $_POST[ $filename ] );
  ?>

how to proceed further by calling the image to by $attach_id from usermeta and displayinf it to user as thumbnail- unable to figure this step

Answer 1

You can't really set a different featured image for post based on a user. There is just one post, therefore only one featured image for it.
If you want to display a different image, based on which user is viewing the post, save that use wp_insert_attachment( $attachment, $filename, 0) to insert attachment without binding it to the post. Then save that $attach_id to the usermeta table. Then, when user is viewing that post, simply get $attach_id with get_user_meta and display that image (you can use wp_get_attachment_url for example) instead of featured image of the post.

UPDATE
First, saving user meta should look like this

update_user_meta($current_user_id, '_avatar_id', $attach_id);

Second, in the beginning, you should check if user is logged in with is_user_logged_in function.

Third, you should check for user had avatar before and remove it (I mean, why store their old one after they have a new one, right?) like so:

$old_attach=get_user_meta($current_user_id, '_avatar_id', true);
if(is_numeric($old_attach))
{
    wp_delete_attachment($old_attach, true);
}

Your final code to save avatar should look like:

if (is_user_logged_in())
{
    $addroot = '/wp-content/uploads/2016/09/';
    $current_user_id = get_current_user_id();
    $extimage = '.jpg';
    $filename = $addroot . $current_user_id . $extimage;
    $filetype = wp_check_filetype(basename($filename), null);
    $wp_upload_dir = wp_upload_dir();
    $attachment = array(
        'guid' => $wp_upload_dir['url'] . '/' . basename($filename),
        'post_mime_type' => $filetype['type'],
        'post_title' => preg_replace('/\.[^.]+$/', '', basename($filename)),
        'post_content' => '',
        'post_status' => 'inherit'
    );
    $attach_id = wp_insert_attachment($attachment, $filename, 0);
    require_once( ABSPATH . 'wp-admin/includes/image.php' );
    wp_update_attachment_metadata($attach_id, wp_generate_attachment_metadata($attach_id, $filename));
    $old_attach = get_user_meta($current_user_id, '_avatar_id', true);
    if (is_numeric($old_attach))
    {
        wp_delete_attachment($old_attach, true);
    }
    update_user_meta($current_user_id, '_avatar_id', $attach_id);
}
else
{
    //show error here or something   
}

Now, to access it, you can write a simple function, like this:

function get_user_avatar()
{
    if (is_user_logged_in())
    {
        $avatar_id = get_user_meta(get_current_user_id(), '_avatar_id', true);
        if (is_numeric($avatar_id))
        {
            return'<img src="' . wp_get_attachment_url($avatar_id) . '"  alt="User avatar"/>';
        }
        else
        {
            return '<img src="url_to_your_default_avatar" alt="User avatar"/>';
        }
    }
    return false;
}