Ticket #23021: 23021.5.diff

Index: wp-includes/functions.php
===================================================================
--- wp-includes/functions.php   (revision 23195)
+++ wp-includes/functions.php   (working copy)
@@ -902,7 +902,6 @@
 function wp_get_nocache_headers() {
        $headers = array(
                'Expires' => 'Wed, 11 Jan 1984 05:00:00 GMT',
-               'Last-Modified' => '',
                'Cache-Control' => 'no-cache, must-revalidate, max-age=0',
                'Pragma' => 'no-cache',
        );
@@ -910,6 +909,10 @@
        if ( function_exists('apply_filters') ) {
                $headers = (array) apply_filters('nocache_headers', $headers);
        }
+
+       if ( isset( $headers['Last-Modified'] ) && empty( $headers['Last-Modified'] ) )
+               unset( $headers['Last-Modified'] ); // The Last-Modified header should not be empty
+
        return $headers;
 }
 
@@ -926,8 +929,6 @@
        $headers = wp_get_nocache_headers();
        foreach( $headers as $name => $field_value )
                @header("{$name}: {$field_value}");
-       if ( empty( $headers['Last-Modified'] ) && function_exists( 'header_remove' ) )
-               @header_remove( 'Last-Modified' );
 }
 
 /**
Index: wp-includes/class-wp.php
===================================================================
--- wp-includes/class-wp.php    (revision 23195)
+++ wp-includes/class-wp.php    (working copy)
@@ -376,14 +376,14 @@
 
                $headers = apply_filters('wp_headers', $headers, $this);
 
+               if ( isset( $headers['Last-Modified'] ) && empty( $headers['Last-Modified'] ) )
+                       unset( $headers['Last-Modified'] ); // The Last-Modified header should not be empty
+
                if ( ! empty( $status ) )
                        status_header( $status );
                foreach( (array) $headers as $name => $field_value )
                        @header("{$name}: {$field_value}");
 
-               if ( isset( $headers['Last-Modified'] ) && empty( $headers['Last-Modified'] ) && function_exists( 'header_remove' ) )
-                       @header_remove( 'Last-Modified' );
-
                if ( $exit_required )
                        exit();