Docs: Update the documentation for `get_post_meta()` to clarify that `$single` has no effect when the `$meta_key` is not provided.

Props chetan200891, titodevera.
Fixes #42687.

Built from https://develop.svn.wordpress.org/trunk@42227


git-svn-id: http://core.svn.wordpress.org/trunk@42056 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-includes/post.php

@@ -1770,7 +1770,9 @@ function delete_post_meta( $post_id, $meta_key, $meta_value = '' ) {
  * @param int    $post_id Post ID.
  * @param string $key     Optional. The meta key to retrieve. By default, returns
  *                        data for all keys. Default empty.
- * @param bool   $single  Optional. Whether to return a single value. Default false.
+ * @param bool   $single  Optional, default is false.
+ *                        If true, return only the first value of the specified meta_key.
+ *                        This parameter has no effect if meta_key is not specified.
  * @return mixed Will be an array if $single is false. Will be value of meta data
  *               field if $single is true.
  */

wp-includes/version.php

@@ -4,7 +4,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '5.0-alpha-42226';
+$wp_version = '5.0-alpha-42227';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.