diff --git a/wp-admin/edit-form-advanced.php b/wp-admin/edit-form-advanced.php
index 59b1c6903f..258a3f78d2 100644
--- a/wp-admin/edit-form-advanced.php
+++ b/wp-admin/edit-form-advanced.php
@@ -13,6 +13,8 @@
  */
 if ( ! isset( $post_ID ) )
 	$post_ID = 0;
+else
+	$post_ID = (int) $post_ID;
 
 $action = isset($action) ? $action : '';
 if ( isset($_GET['message']) )
@@ -36,10 +38,9 @@ if ( 0 == $post_ID ) {
 	$form_extra = "<input type='hidden' id='post_ID' name='temp_ID' value='$temp_ID' />";
 	$autosave = false;
 } else {
-	$post_ID = (int) $post_ID;
 	$form_action = 'editpost';
 	$form_extra = "<input type='hidden' id='post_ID' name='post_ID' value='$post_ID' />";
-	$autosave = wp_get_post_autosave( $post_id );
+	$autosave = wp_get_post_autosave( $post_ID );
 
 	// Detect if there exists an autosave newer than the post and if that autosave is different than the post
 	if ( $autosave && mysql2date( 'U', $autosave->post_modified_gmt ) > mysql2date( 'U', $post->post_modified_gmt ) ) {
diff --git a/wp-admin/includes/post.php b/wp-admin/includes/post.php
index a48e575b85..4e83a1a6c6 100644
--- a/wp-admin/includes/post.php
+++ b/wp-admin/includes/post.php
@@ -17,7 +17,8 @@ function _wp_translate_postdata( $update = false ) {
 	$_POST['post_content'] = $_POST['content'];
 	$_POST['post_excerpt'] = $_POST['excerpt'];
 	$_POST['post_parent'] = isset($_POST['parent_id'])? $_POST['parent_id'] : '';
-	$_POST['to_ping'] = $_POST['trackback_url'];
+	if ( isset($_POST['trackback_url']) )
+		$_POST['to_ping'] = $_POST['trackback_url'];
 
 	if (!empty ( $_POST['post_author_override'] ) ) {
 		$_POST['post_author'] = (int) $_POST['post_author_override'];
@@ -29,7 +30,7 @@ function _wp_translate_postdata( $update = false ) {
 		}
 	}
 
-	if ( $_POST['post_author'] != $_POST['user_ID'] ) {
+	if ( isset($_POST['user_ID']) && ($_POST['post_author'] != $_POST['user_ID']) ) {
 		if ( 'page' == $_POST['post_type'] ) {
 			if ( !current_user_can( 'edit_others_pages' ) ) {
 				return new WP_Error( 'edit_others_pages', $update ?
@@ -66,7 +67,7 @@ function _wp_translate_postdata( $update = false ) {
 			if ( $previous_status != 'publish' OR !current_user_can( 'edit_published_pages') )
 				$_POST['post_status'] = 'pending';
 	} else {
-		if ( 'publish' == $_POST['post_status'] && !current_user_can( 'publish_posts' ) ) :
+		if ( isset($_POST['post_status']) && ('publish' == $_POST['post_status'] && !current_user_can( 'publish_posts' )) ) :
 			// Stop attempts to publish new posts, but allow already published posts to be saved if appropriate.
 			if ( $previous_status != 'publish' OR !current_user_can( 'edit_published_posts') )
 				$_POST['post_status'] = 'pending';
diff --git a/wp-admin/includes/template.php b/wp-admin/includes/template.php
index 8e19eca536..4e05c746df 100644
--- a/wp-admin/includes/template.php
+++ b/wp-admin/includes/template.php
@@ -917,7 +917,7 @@ function user_row( $user_object, $style = '', $role = '' ) {
 	} else {
 		$edit = $user_object->user_login;
 	}
-	$role_name = $wp_roles->role_names[$role] ? translate_with_context($wp_roles->role_names[$role]) : __('None');
+	$role_name = isset($wp_roles->role_names[$role]) ? translate_with_context($wp_roles->role_names[$role]) : __('None');
 	$r = "<tr id='user-$user_object->ID'$style>
 		<th scope='row' class='check-column'><input type='checkbox' name='users[]' id='user_{$user_object->ID}' class='$role' value='{$user_object->ID}' /></th>
 		<td><strong>$edit</strong></td>
@@ -1530,19 +1530,21 @@ function do_meta_boxes($page, $context, $object) {
 			break;
 
 		foreach ( array('high', 'sorted', 'core', 'default', 'low') as $priority ) {
-			foreach ( (array) $wp_meta_boxes[$page][$context][$priority] as $box ) {
-				if ( false == $box || ! $box['title'] )
-					continue;
-				$i++;
-				$style = '';
-				if ( in_array($box['id'], $hidden) )
-					$style = 'style="display:none;"';
-				echo '<div id="' . $box['id'] . '" class="postbox ' . postbox_classes($box['id'], $page) . '" ' . $style . '>' . "\n";
-				echo "<h3><span class='hndle'>{$box['title']}</span></h3>\n";
-				echo '<div class="inside">' . "\n";
-				call_user_func($box['callback'], $object, $box);
-				echo "</div>\n";
-				echo "</div>\n";
+			if ( isset($wp_meta_boxes[$page][$context][$priority]) ) {
+				foreach ( (array) $wp_meta_boxes[$page][$context][$priority] as $box ) {
+					if ( false == $box || ! $box['title'] )
+						continue;
+					$i++;
+					$style = '';
+					if ( in_array($box['id'], $hidden) )
+						$style = 'style="display:none;"';
+					echo '<div id="' . $box['id'] . '" class="postbox ' . postbox_classes($box['id'], $page) . '" ' . $style . '>' . "\n";
+					echo "<h3><span class='hndle'>{$box['title']}</span></h3>\n";
+					echo '<div class="inside">' . "\n";
+					call_user_func($box['callback'], $object, $box);
+					echo "</div>\n";
+					echo "</div>\n";
+				}
 			}
 		}
 	} while(0);
diff --git a/wp-admin/revision.php b/wp-admin/revision.php
index 3b21e72471..c93357cc36 100644
--- a/wp-admin/revision.php
+++ b/wp-admin/revision.php
@@ -9,7 +9,7 @@
 /** WordPress Administration Bootstrap */
 require_once('admin.php');
 
-wp_reset_vars(array('revision', 'left', 'right', 'action'));
+wp_reset_vars(array('revision', 'left', 'right', 'diff', 'action'));
 $revision_id = absint($revision);
 $diff        = absint($diff);
 $left        = absint($left);
diff --git a/wp-includes/canonical.php b/wp-includes/canonical.php
index 1671b44285..c23cbfbe02 100644
--- a/wp-includes/canonical.php
+++ b/wp-includes/canonical.php
@@ -156,11 +156,13 @@ function redirect_canonical($requested_url=null, $do_redirect=true) {
 	// Remove trailing spaces from the path
 	$redirect['path'] = preg_replace( '#(%20| )+$#', '', $redirect['path'] );
 
-	// Remove trailing slashes from certain terminating query string args
-	$redirect['query'] = preg_replace( '#((p|page_id|cat|tag)=[^&]*?)(%20| )+$#', '$1', $redirect['query'] );
+	if ( isset( $redirect['query'] ) ) {
+		// Remove trailing slashes from certain terminating query string args
+		$redirect['query'] = preg_replace( '#((p|page_id|cat|tag)=[^&]*?)(%20| )+$#', '$1', $redirect['query'] );
 
-	// Clean up empty query strings
-	$redirect['query'] = preg_replace( '#&?(p|page_id|cat|tag)=?$#', '', $redirect['query'] );
+		// Clean up empty query strings
+		$redirect['query'] = preg_replace( '#&?(p|page_id|cat|tag)=?$#', '', $redirect['query'] );
+	}
 
 	// strip /index.php/ when we're not using PATHINFO permalinks
 	if ( !$wp_rewrite->using_index_permalinks() )
diff --git a/wp-includes/post.php b/wp-includes/post.php
index ee9362a4a9..3da3999f7d 100644
--- a/wp-includes/post.php
+++ b/wp-includes/post.php
@@ -123,8 +123,10 @@ function &get_children($args = '', $output = OBJECT) {
 	$r = wp_parse_args( $args, $defaults );
 
 	$children = get_posts( $r );
-	if ( !$children )
-		return false;
+	if ( !$children ) {
+		$kids = false;
+		return $kids;
+	}
 
 	update_post_cache($children);
 
@@ -776,9 +778,13 @@ function sanitize_post($post, $context = 'display') {
 	if ( 'raw' == $context )
 		return $post;
 	if ( is_object($post) ) {
+		if ( !isset($post->ID) )
+			$post->ID = 0;
 		foreach ( array_keys(get_object_vars($post)) as $field )
 			$post->$field = sanitize_post_field($field, $post->$field, $post->ID, $context);
 	} else {
+		if ( !isset($post['ID']) )
+			$post['ID'] = 0;
 		foreach ( array_keys($post) as $field )
 			$post[$field] = sanitize_post_field($field, $post[$field], $post['ID'], $context);
 	}
@@ -1316,7 +1322,7 @@ function wp_insert_post($postarr = array(), $wp_error = false) {
 	}
 
 	// Make sure we set a valid category
-	if (0 == count($post_category) || !is_array($post_category)) {
+	if ( empty($post_category) || 0 == count($post_category) || !is_array($post_category) ) {
 		$post_category = array(get_option('default_category'));
 	}
 
@@ -1329,6 +1335,8 @@ function wp_insert_post($postarr = array(), $wp_error = false) {
 	if ( empty($post_type) )
 		$post_type = 'post';
 
+	$post_ID = 0;
+
 	// Get the post ID and GUID
 	if ( $update ) {
 		$post_ID = (int) $ID;
@@ -1432,7 +1440,8 @@ function wp_insert_post($postarr = array(), $wp_error = false) {
 				return 0;
 		}
 	} else {
-		$data['post_mime_type'] = stripslashes( $post_mime_type ); // This isn't in the update
+		if ( isset($post_mime_type) )
+			$data['post_mime_type'] = stripslashes( $post_mime_type ); // This isn't in the update
 		if ( false === $wpdb->insert( $wpdb->posts, $data ) ) {
 			if ( $wp_error )
 				return new WP_Error('db_insert_error', __('Could not insert post into the database'), $wpdb->last_error);
diff --git a/wp-includes/taxonomy.php b/wp-includes/taxonomy.php
index 684d5aa376..fc39a7c436 100644
--- a/wp-includes/taxonomy.php
+++ b/wp-includes/taxonomy.php
@@ -609,8 +609,10 @@ function &get_terms($taxonomies, $args = '') {
 	$key = md5( serialize( compact(array_keys($defaults)) ) . serialize( $taxonomies ) . $filter_key );
 
 	if ( $cache = wp_cache_get( 'get_terms', 'terms' ) ) {
-		if ( isset( $cache[ $key ] ) )
-			return apply_filters('get_terms', $cache[$key], $taxonomies, $args);
+		if ( isset( $cache[ $key ] ) ) {
+			$terms = apply_filters('get_terms', $cache[$key], $taxonomies, $args);
+			return $terms;
+		}
 	}
 
 	if ( 'count' == $orderby )