Rebuilds WordPress image metadata after a manual media library migration

rebuild_image_metadata.php

<?php
//Source: http://www.adam-makes-websites.com/discoveries/fixing_messed_up_image_attachments_in_wordpress_that_have_no_postmeta_values
function fixWPImageMetaData() {

	// Notes:
	//  1) This function will not alter existing meta entries for your images.  The function is to ADD meta data for the images
	//     without it due to manually importing them or some other kind of mess-up in your wordpress wp_postmeta table.
	//  2) Always remember to take a full database backup before each run of the function!
	//  3) Although only tested on fairly recent WP versions it may work as far back as v1.5+.  Give it a go and let me know!

	// Usage:
	// 1) Backup your database.  Also look in wp_postmeta with a database tool.  Order by meta_id DESC and make a note of the highest
	//    meta_id value at the top of the results.  This is useful in case you want to undo changes added by the function.
	//    Remember, this function only updates the wp_postmeta table.
	// 2) First reference the function in a page within the frontend of your theme!
	//    You can call the function within your themes functions.php file but don't refresh an admin page as the relative
	//    paths will be wrong and the function will fail.
	// 3) With the $test_run set to true check the path settings and then run the file and read the debug output on screen.
	//    If it looks all ok and the file paths correct set test_run to false and run once more!
	// 4) After running the function once with the $test_run set to false comment out your call to the function and check your
	//    results!  Hopefully new images or images with their thumbnails will now appear in the Media page of the WP admin.


	// settings
	$test_run=true;		// set this to false AFTER your happy with the results

	// the paths - check these and ensure they both end with a forward slash!
	$full_url_to_upload_folder_root=array("http://localhost/wp-content/uploads/", "http://localhost/wordpress/wp-content/uploads/");	// this will definitely need updating for your install!
	$local_path_to_uploads="wp-content/uploads/";					// this is the path relative to the base WP folder


	global $wpdb;

	$sql = "select ID from {$wpdb->posts}
	where post_type = 'attachment'
	and post_mime_type like 'image/%'";
	$images = $wpdb->get_col($sql);

	foreach ($images as $id) {

		$run=false;

		echo "<br>Reading meta for attachment ID: ".$id."...<br>";
		$meta = wp_get_attachment_metadata($id);


		if (!$meta) {
			echo "No meta data for attachment ID: ".$id."...<br>";
			$file = get_attached_file($id);

			if (empty($file) || $file==""){
				// if this fails try to get filename from post and check it exists
				$sql2 = "select guid from {$wpdb->posts}
					where ID=$id";
				$imageSearch = $wpdb->get_col($sql2);
				if ( !empty($imageSearch) && $imageSearch[0]!=""){
					$foundImage=$imageSearch[0];
					$foundImage=str_replace($full_url_to_upload_folder_root,"",$foundImage);

					// check it exists!
					if (file_exists($local_path_to_uploads.$foundImage)){
						$run=true;
						$file=$local_path_to_uploads.$foundImage;
						echo "I've checked for file manually ('".$local_path_to_uploads.$foundImage."') and it exists so can resolve!<br>";
					}else{
						echo "I've checked for file manually ('".$local_path_to_uploads.$foundImage."') but doesn't exist at this location so ignoring.<br>";
					}
				}

			}else{
				$run=true;
			}

			if ($run===true&&$test_run!==true) {
				echo "Adding new meta data for attachment ID: ".$id."...<br>";

				// add first meta entry with image properties...
				$info = getimagesize($file);
				$file_for_insert=str_replace($local_path_to_uploads,"",$file);
				$meta = array (
					'width' => $info[0],
					'height' => $info[1],
					'hwstring_small' => "height='{$info[1]}' width='{$info[0]}'",
					'file' => ($file_for_insert),
					'sizes' => array(),         // thumbnails etc.
					'image_meta' => array(),    // EXIF data
				);
				update_post_meta($id, '_wp_attachment_metadata', $meta);

				// add a second meta entry for the local path to the file...
				update_post_meta($id, '_wp_attached_file', $file_for_insert);

			}
		}
    }

}

//Source: http://wordpress.stackexchange.com/questions/9870/how-do-you-create-a-virtual-page-in-wordpress
add_action( 'init', 'wpse9870_init_internal' );
function wpse9870_init_internal()
{
    add_rewrite_rule( 'new-thumb', 'index.php?wpse9870_api=1', 'top' );
}

add_filter( 'query_vars', 'wpse9870_query_vars' );
function wpse9870_query_vars( $query_vars )
{
    $query_vars[] = 'wpse9870_api';
    return $query_vars;
}

add_action( 'parse_request', 'wpse9870_parse_request' );
function wpse9870_parse_request( &$wp )
{
    if ( array_key_exists( 'wpse9870_api', $wp->query_vars ) ) {
        fixWPImageMetaData();
        exit();
    }
    return;
}