add user meta for featured image - php

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;
}