Allow users to remove images they have uploaded

I created an account on your site and uploaded an image to populate the “Gallery”. I think The solution below will work for you.

I have updated the example plugin created for your earlier topic to support file deletion. To enable the new feature you must add another parameter to your [mla_gallery] shortcode, e.g.:

[mla_gallery author=current my_filter='allow file deletion']

Once that’s done the file name will be displayed below each thumbnail image with a link labeled “Delete this file.” If you click on the link, the associated file will be deleted and the gallery display will refresh with an appropriate message above the gallery.

Here is the complete source code for the updated plugin:

<?php
/*
Plugin Name: MLA Current User Example
Plugin URI: http://fairtradejudaica.org/media-library-assistant-a-wordpress-plugin/
Description: Uses the current logged in user to supply an "Author" parameter for the query
Author: David Lingren
Version: 1.01
Author URI: http://fairtradejudaica.org/our-story/staff/

Copyright 2016 David Lingren

    This program is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
    the Free Software Foundation; either version 2 of the License, or
    (at your option) any later version.

    This program is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.

    You can get a copy of the GNU General Public License by writing to the
    Free Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110, USA
*/

/**
 * Class MLA Current User Example uses the current logged in user to supply an "Author" parameter for the query
 *
 * @package MLA Current User Example
 * @since 1.00
 */
class MLACurrentUserExample {
    /**
     * Initialization function, similar to __construct()
     *
     * @since 1.00
     */
    public static function initialize() {
        // The filters are only useful for front-end posts/pages; exit if in the admin section
        if ( is_admin() )
            return;

        add_filter( 'mla_gallery_raw_attributes', 'MLACurrentUserExample::mla_gallery_raw_attributes_filter', 10, 1 );
        add_filter( 'mla_gallery_attributes', 'MLACurrentUserExample::mla_gallery_attributes_filter', 10, 1 );
        add_filter( 'mla_gallery_open_template', 'MLACurrentUserExample::mla_gallery_open_template_filter', 10, 1 );
        add_filter( 'mla_gallery_item_values', 'MLACurrentUserExample::mla_gallery_item_values_filter', 10, 1 );
    }

    /**
     * Save the shortcode attributes
     *
     * @since 1.01
     *
     * @var    array
     */
    private static $shortcode_attributes = array();

    /**
     * MLA Gallery Raw (Display) Attributes
     *
     * @since 1.01
     *
     * @param    array    the raw shortcode parameters passed in to the shortcode
     */
    public static function mla_gallery_raw_attributes_filter( $shortcode_attributes ) {
        error_log( 'MLAGalleryHooksExample::mla_gallery_raw_attributes_filter $shortcode_attributes = ' . var_export( $shortcode_attributes, true ), 0 );

        // Delete the selected file.
        if ( isset( $shortcode_attributes['my_filter'] ) && 'allow file deletion' == $shortcode_attributes['my_filter'] ) {
            if ( isset( $_REQUEST['attachment_ID'] ) ) {
                $id = (integer) $_REQUEST['attachment_ID'];
                if ( current_user_can( 'delete_post', $id ) ) {
                    $result = wp_delete_attachment( $id );
                } else {
                    $result = false;
                }

                if ( ( false === $result ) || ( NULL === $result ) ) {
                    $shortcode_attributes['gallery_open_message'] = "Could not delete attachment_ID '{$id}'.";
                } else {
                    $result = (array) $result; // Some wp_delete_attachment calls return an object
                    $shortcode_attributes['gallery_open_message'] = "Attachment '{$result['post_title']}' (ID {$id}) has been deleted.";
                }

                unset( $_REQUEST['attachment_ID'] );
            }
        }

        return $shortcode_attributes;
    } // mla_gallery_raw_attributes_filter

    /**
     * MLA Gallery (Display) Attributes
     *
     * @since 1.00
     *
     * @param    array    the shortcode parameters passed in to the shortcode
     */
    public static function mla_gallery_attributes_filter( $shortcode_attributes ) {
        global $wpdb;

        // ignore shortcodes without the author parameter set to "current"
        if ( empty( $shortcode_attributes['author'] ) || ( 'current' !== $shortcode_attributes['author'] ) ) {
            return $shortcode_attributes;
        }

        // ignore shortcodes with no logged in user
        $current_user = wp_get_current_user();
        if ( !( $current_user instanceof WP_User ) || ( 0 == $current_user->ID ) ) {
            unset ( $shortcode_attributes['author'] );
        } else {
            $shortcode_attributes['author'] = $current_user->ID;
        }

        // Save the attributes for use in the later filters
        self::$shortcode_attributes = $shortcode_attributes;

        return $shortcode_attributes;
    } // mla_gallery_attributes_filter

    /**
     * Replace the caption value and update captiontag_content as well
     *
     * @since 1.01
     *
     * @param    array    parameter_name => parameter_value pairs
     * @param    string    New value for Caption
     *
     * @return    array    item_values with updated 'caption' and 'captiontag_content'
     */
    private static function _update_caption( $item_values, $new_caption ) {
        $old_caption = $item_values['caption'];
        $item_values['caption'] = $new_caption;

        if ( !empty( $item_values['captiontag_content'] ) ) {
            $item_values['captiontag_content'] = str_replace( $old_caption, $new_caption, $item_values['captiontag_content'] );
        } else {
            if ( $item_values['captiontag'] ) {
                $item_values['captiontag_content'] = '<' . $item_values['captiontag'] . " class='wp-caption-text gallery-caption' id='" . $item_values['selector'] . '-' . $item_values['attachment_ID'] . "'>\n\t\t" . $new_caption . "\n\t</" . $item_values['captiontag'] . ">\n";
            } else {
                $item_values['captiontag_content'] = $new_caption;
            }
        }

        return $item_values;
    } // _update_caption

    /**
     * MLA Gallery Open Template
     *
     * @since 1.01
     *
     * @param    string    template used to generate the HTML markup
     */
    public static function mla_gallery_open_template_filter( $open_template ) {
        // Check for a display message
        if ( isset( self::$shortcode_attributes['gallery_open_message'] ) ) {
            $open_template = '<p><strong>' . self::$shortcode_attributes['gallery_open_message'] . '</strong></p>' . $open_template;
        }

        return $open_template;
    } // mla_gallery_open_template_filter

    /**
     * MLA Gallery Item Values
     *
     * @since 1.01
     *
     * @param    array    parameter_name => parameter_value pairs
     */
    public static function mla_gallery_item_values_filter( $item_values ) {
        error_log( 'MLAGalleryHooksExample::mla_gallery_item_values_filter $item_values = ' . var_export( $item_values, true ), 0 );

        if ( isset( self::$shortcode_attributes['my_filter'] ) && ( 'allow file deletion' == self::$shortcode_attributes['my_filter'] ) ) {
            $id = (integer) $item_values['attachment_ID'];
        error_log( 'MLAGalleryHooksExample::mla_gallery_item_values_filter $id = ' . var_export( $id, true ), 0 );
            if ( current_user_can( 'delete_post', $id ) ) {
                // Compose a new caption, adding the deletion link.
                $mla_link_href = "{$item_values['page_url']}?attachment_ID={$id}";
                $item_values = self::_update_caption( $item_values, sprintf( '%1$s<br><a href="%2$s" title="Click to delete">Delete this file</a>', $item_values['base_file'], $mla_link_href ) );
            } else {
                $item_values = self::_update_caption( $item_values, sprintf( '%1$s', $item_values['base_file'] ) );
            }
        }

        return $item_values;
    } // mla_gallery_item_values_filter
} // Class MLACurrentUserExample

/*
 * Install the filters at an early opportunity
 */
add_action('init', 'MLACurrentUserExample::initialize');
?>

Give it a try and let me know how it works for you. I am marking this topic resolved, but please update it if you have any problems or further questions regarding the updated example plugin.