我有这个方法（谢谢Mridul）：

function MediaFileAlreadyExists($filename){
    global $wpdb;
    $query = "SELECT COUNT(*) FROM {$wpdb->postmeta} WHERE meta_value LIKE \'%/$filename\'";
    return ($wpdb->get_var($query)  > 0) ;
}

// MediaFileAlreadyExists("my-image.png");

我知道这是一个老问题，但我不喜欢这些答案，所以这里是我的解决方案。

这将检查文件是否存在。如果是，将更新现有附件；如果没有，它将创建一个新附件。

// Get upload dir
$upload_dir    = wp_upload_dir();
$upload_folder = $upload_dir[\'path\'];

// Set filename, incl path
$filename = "{$upload_folder}/myfile-{$id}.pdf";

// Check the type of file. We\'ll use this as the \'post_mime_type\'.
$filetype = wp_check_filetype( basename( $filename ), null );

// Get file title
$title = preg_replace( \'/\\.[^.]+$/\', \'\', basename( $filename ) );

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

// Does the attachment already exist ?
if( post_exists( $title ) ){
  $attachment = get_page_by_title( $title, OBJECT, \'attachment\');
  if( !empty( $attachment ) ){
    $attachment_data[\'ID\'] = $attachment->ID;
  }
}

// If no parent id is set, reset to default(0)
if( empty( $parent_id ) ){
  $parent_id = 0;
}

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

// 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 );

您可以检查图像是否存在post_exists($filename) . 如果图像存在，您可以更新它，也可以创建它

 //if image exist update else create it
        if (post_exists($filename)){
                $page = get_page_by_title($filename, OBJECT, \'attachment\');
                $attach_id = $page->ID;

                $attach_data = wp_generate_attachment_metadata( $attach_id, $destination ); // Generate attachment data, filesize, height, width etc.

                wp_update_attachment_metadata( $attach_id, $attach_data ); // Add the above meta data

                add_post_meta($attach_id, \'_wp_attachment_image_alt\', $filealt); // Add the alt text 
        }
        else{

                $attach_id = wp_insert_attachment( $attachment, $destination, $post_id ); 

                $attach_data = wp_generate_attachment_metadata( $attach_id, $destination ); 

                wp_update_attachment_metadata( $attach_id, $attach_data ); 

                add_post_meta($attach_id, \'_wp_attachment_image_alt\', $filealt); 
            }

我还没试过呢。但应该这么简单：

post_exists( $filename, \'\', \'\', \'attachment\' );

此函数将媒体文件名作为参数，如果存在，则返回meta\\u id，否则返回（false）。

function MediaFileAlreadyExists($filename){
    global $wpdb;
    $query = "SELECT meta_id FROM {$wpdb->postmeta} WHERE meta_value LIKE \'%/$filename\'";

    if ( $wpdb->get_var($query) ){
        return $wpdb->get_var($query);
    }

    return false;
}