Get rid of wp_cache_key(), as it's not really that useful. See [15838]

git-svn-id: http://svn.automattic.com/wordpress/trunk@15839 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-includes/functions.php

@@ -279,24 +279,6 @@ function is_serialized_string( $data ) {
 	return false;
 }
 
-/**
- * Generates a unique key from an argument
- * 
- * @since 3.1
- *
- * @param mixed $arg
- * @return string
- */
-function wp_cache_key( $arg ) {
-	if ( is_scalar( $arg ) )
-		return md5( $arg );
-
-	$arg = (array) $arg;
-	sort( $arg );
-
-	return md5( serialize( $arg ) );
-}
-
 /**
  * Retrieve option value based on name of option.
  *

wp-includes/post.php

@@ -3989,7 +3989,7 @@ function _get_last_post_time( $timezone, $field ) {
 
 	$post_types = apply_filters( "get_lastpost{$field}_post_types", (array) $post_types );
 
-	$key = "lastpost{$field}:$blog_id:$timezone:" . wp_cache_key( $post_types );
+	$key = "lastpost{$field}:$blog_id:$timezone:" . md5( serialize( $post_types ) );
 
 	$date = wp_cache_get( $key, 'timeinfo' );