diff -r 3d4e9c994f10 -r a86126ab1dd4 wp/wp-admin/includes/taxonomy.php
--- a/wp/wp-admin/includes/taxonomy.php	Tue Oct 22 16:11:46 2019 +0200
+++ b/wp/wp-admin/includes/taxonomy.php	Tue Dec 15 13:49:49 2020 +0100
@@ -7,7 +7,7 @@
  */
 
 //
-// Category
+// Category.
 //
 
 /**
@@ -53,7 +53,8 @@
  * @return int|WP_Error
  */
 function wp_create_category( $cat_name, $parent = 0 ) {
-	if ( $id = category_exists( $cat_name, $parent ) ) {
+	$id = category_exists( $cat_name, $parent );
+	if ( $id ) {
 		return $id;
 	}
 
@@ -72,15 +73,19 @@
  *
  * @param string[] $categories Array of category names to create.
  * @param int      $post_id    Optional. The post ID. Default empty.
- * @return array List of categories to create for the given post.
+ * @return int[] Array of IDs of categories assigned to the given post.
  */
 function wp_create_categories( $categories, $post_id = '' ) {
 	$cat_ids = array();
 	foreach ( $categories as $category ) {
-		if ( $id = category_exists( $category ) ) {
+		$id = category_exists( $category );
+		if ( $id ) {
 			$cat_ids[] = $id;
-		} elseif ( $id = wp_create_category( $category ) ) {
-			$cat_ids[] = $id;
+		} else {
+			$id = wp_create_category( $category );
+			if ( $id ) {
+				$cat_ids[] = $id;
+			}
 		}
 	}
 
@@ -124,7 +129,7 @@
 	);
 	$catarr       = wp_parse_args( $catarr, $cat_defaults );
 
-	if ( trim( $catarr['cat_name'] ) == '' ) {
+	if ( '' === trim( $catarr['cat_name'] ) ) {
 		if ( ! $wp_error ) {
 			return 0;
 		} else {
@@ -187,7 +192,7 @@
 		return false;
 	}
 
-	// First, get all of the original fields
+	// First, get all of the original fields.
 	$category = get_term( $cat_ID, 'category', ARRAY_A );
 	_make_cat_compat( $category );
 
@@ -201,7 +206,7 @@
 }
 
 //
-// Tags
+// Tags.
 //
 
 /**
@@ -295,12 +300,13 @@
  *
  * @since 2.8.0
  *
- * @param int|string $tag_name
- * @param string $taxonomy Optional. The taxonomy for which to retrieve terms. Default 'post_tag'.
+ * @param string $tag_name The term name.
+ * @param string $taxonomy Optional. The taxonomy within which to create the term. Default 'post_tag'.
  * @return array|WP_Error
  */
 function wp_create_term( $tag_name, $taxonomy = 'post_tag' ) {
-	if ( $id = term_exists( $tag_name, $taxonomy ) ) {
+	$id = term_exists( $tag_name, $taxonomy );
+	if ( $id ) {
 		return $id;
 	}