我建议您使用更新的media manager对话框；WordPress将处理所有图像上传内容，包括生成中间大小和附加元数据。

这里是一个工作示例（这是一个根据以前的代码构建的快速示例，可能需要在生产中使用一些调整）：

add_action( \'admin_enqueue_scripts\', \'load_wp_media_files\' );
function load_wp_media_files( $page ) {
  if( $page == \'profile.php\' || $page == \'user-edit.php\' ) {
    wp_enqueue_media();
    wp_enqueue_script( \'my_custom_script\', plugins_url( \'/js/myscript.js\' , __FILE__ ), array(\'jquery\'), \'0.1\' );
  }
}

add_action( \'show_user_profile\', \'cover_image_function\' );
add_action( \'edit_user_profile\', \'cover_image_function\' );
function cover_image_function( $user ) 
{
    $image_id = get_user_meta( $user->ID, \'mycoverimage\', true );
    if( intval( $image_id ) > 0 ) {
        // Change with the image size you want to use
        $image = wp_get_attachment_image( $image_id, \'medium\', false, array( \'id\' => \'user-preview-image\' ) );
    } else {
        $image = \'<img id="user-preview-image" src="https://some.default.image.jpg" />\';
    }
    ?>
   <h3>Cover Image</h3>
   <style type="text/css">
    .fh-profile-upload-options th,
    .fh-profile-upload-options td,
    .fh-profile-upload-options input {
        vertical-align: top;
    }
    .user-preview-image {
        display: block;
        height: auto;
        width: 300px;
    }
    </style>
    <table class="form-table fh-profile-upload-options">
        <tr>
            <th>
                <label for="image">Cover Image</label>
            </th>
            <td>
                <?php echo $image; ?>
                <input type="hidden" name="mycoverimage" id="mycoverimage" value="<?php echo esc_attr( get_the_author_meta( \'mycoverimage\', $user->ID ) ); ?>" class="regular-text" />
                <input type=\'button\' class="button-primary" value="Upload Image" id="coverimage"/><br />
                <span class="description">Please upload your cover image.</span>
            </td>
        </tr>
    </table>
    <?php
}

add_action( \'personal_options_update\', \'save_cover_image\' );
add_action( \'edit_user_profile_update\', \'save_cover_image\' );
function save_cover_image( $user_id ) {
    if ( ! current_user_can( \'edit_user\', $user_id ) )
    {
        return false;
    }

    update_user_meta( $user_id, \'mycoverimage\', $_POST[ \'mycoverimage\' ] );
}  


// Ajax action to refresh the user image
add_action( \'wp_ajax_cyb_get_image_url\', \'cyb_get_image_url\'   );
function cyb_get_image_url() {
    if(isset($_GET[\'id\']) ){
        $image = wp_get_attachment_image( filter_input( INPUT_GET, \'id\', FILTER_VALIDATE_INT ), \'medium\', false, array( \'id\' => \'user-preview-image\' ) );
        $data = array(
            \'image\'    => $image,
        );
        wp_send_json_success( $data );
    } else {
        wp_send_json_error();
    }
}

jQuery(document).ready( function($) {

      jQuery(\'input#coverimage\').click(function(e) {

             e.preventDefault();
             var image_frame;
             if(image_frame){
                 image_frame.open();
             }
             image_frame = wp.media({
                           title: \'Select Media\',
                           multiple : false,
                           library : {
                                type : \'image\',
                            }
                       });

                       image_frame.on(\'close\',function() {
                          // get selections and save to hidden input plus other AJAX stuff etc.
                          var selection =  image_frame.state().get(\'selection\');
                          var gallery_ids = new Array();
                          var my_index = 0;
                          selection.each(function(attachment) {
                             gallery_ids[my_index] = attachment[\'id\'];
                             my_index++;
                          });
                          var ids = gallery_ids.join(",");
                          jQuery(\'input#mycoverimage\').val(ids);
                          Refresh_Image(ids);
                       });

                      image_frame.on(\'open\',function() {
                        var selection =  image_frame.state().get(\'selection\');
                        ids = jQuery(\'input#mycoverimage\').val().split(\',\');
                        ids.forEach(function(id) {
                          attachment = wp.media.attachment(id);
                          attachment.fetch();
                          selection.add( attachment ? [ attachment ] : [] );
                        });

                      });

                    image_frame.on(\'toolbar:create:select\',function() {

                        image_frame.state().set(\'filterable\', \'uploaded\');

                    });

                    image_frame.open();
     });

});

function Refresh_Image(the_id){
        var data = {
            action: \'cyb_get_image_url\',
            id: the_id
        };

        jQuery.get(ajaxurl, data, function(response) {

            if(response.success === true) {
                jQuery(\'#user-preview-image\').replaceWith( response.data.image );
            }
        });
}

$image_id = get_user_meta( $user->ID, \'mycoverimage\', true );
$fulle_user_image = wp_get_attachment_image( $image_id, \'full\' );

不确定这会有什么不同，但因为你只想得到一个值get_var 而不是get_col. 我稍微调整了查询，使其符合我所知道的效果：

function get_attachment_id($image_url) {
    global $wpdb;
    $attachment = $wpdb->get_var($wpdb->prepare("SELECT ID FROM ".$wpdb->prefix."posts WHERE post_type=\'attachment\' AND guid=\'%s\'", $image_url )); 
    return $attachment; 
}

EDIT 您可以尝试将URL路径与guid 而不是完整的URL：

function get_attachment_id($image_url) {
    $parseurl = parse_url($image_url);
    $path = $parseurl[\'path\'];

    global $wpdb;
    $attachments = $wpdb->get_results("SELECT ID,guid FROM ".$wpdb->prefix."posts WHERE post_type=\'attachment\'");
    foreach ($attachments as $attachment) {
        if (strstr($attachment->guid,$path)) {return $attachment->ID;}
    }
    echo "<!-- All Attachments "; print_r($attachments); echo "-->"; // debug output
}