From 7fc579eec961f2c8af01957402686bcfe5ebaaad Mon Sep 17 00:00:00 2001
From: Gary Pendergast <pento@git.wordpress.org>
Date: Tue, 30 Aug 2016 07:37:59 +0000
Subject: [PATCH] Database: Don't force an unsupported character set that
 previously would've silently failed.

[37320] corrected some behaviour in how PHP and MySQL character sets are matched up. This was correct, but had the side effect of causing some incorrectly configured sites to start failing.

Prior to [37320], if `DB_CHARSET` was set to `utf8mb4`, but the PHP version didn't support `utf8mb4`, it would fall back to the default character set - usually `latin1`. After [37320], the `SET NAMES` query would force MySQL to treat the connection character set as `utf8mb4`, even if PHP wasn't able to understand it.

By checking if `mysqli_set_charset()` succeeded, we can simulate the old behaviour, while maintaining the fix in [37320].

Props danielkanchev fo helping to diagnose this issue.
Fixes #37689 for trunk.



git-svn-id: https://develop.svn.wordpress.org/trunk@38441 602fd350-edb4-49c9-b593-d223f7449a82
---
 src/wp-includes/wp-db.php | 27 +++++++++++++++++----------
 1 file changed, 17 insertions(+), 10 deletions(-)

diff --git a/src/wp-includes/wp-db.php b/src/wp-includes/wp-db.php
index 3c07900a72..02577b910d 100644
--- a/src/wp-includes/wp-db.php
+++ b/src/wp-includes/wp-db.php
@@ -811,22 +811,29 @@ class wpdb {
 		if ( ! isset( $collate ) )
 			$collate = $this->collate;
 		if ( $this->has_cap( 'collation' ) && ! empty( $charset ) ) {
+			$set_charset_succeeded = true;
+
 			if ( $this->use_mysqli ) {
 				if ( function_exists( 'mysqli_set_charset' ) && $this->has_cap( 'set_charset' ) ) {
-					mysqli_set_charset( $dbh, $charset );
+					$set_charset_succeeded = mysqli_set_charset( $dbh, $charset );
+				}
+
+				if ( $set_charset_succeeded ) {
+					$query = $this->prepare( 'SET NAMES %s', $charset );
+					if ( ! empty( $collate ) )
+						$query .= $this->prepare( ' COLLATE %s', $collate );
+					mysqli_query( $dbh, $query );
 				}
-				$query = $this->prepare( 'SET NAMES %s', $charset );
-				if ( ! empty( $collate ) )
-					$query .= $this->prepare( ' COLLATE %s', $collate );
-				mysqli_query( $dbh, $query );
 			} else {
 				if ( function_exists( 'mysql_set_charset' ) && $this->has_cap( 'set_charset' ) ) {
-					mysql_set_charset( $charset, $dbh );
+					$set_charset_succeeded = mysql_set_charset( $charset, $dbh );
+				}
+				if ( $set_charset_succeeded ) {
+					$query = $this->prepare( 'SET NAMES %s', $charset );
+					if ( ! empty( $collate ) )
+						$query .= $this->prepare( ' COLLATE %s', $collate );
+					mysql_query( $query, $dbh );
 				}
-				$query = $this->prepare( 'SET NAMES %s', $charset );
-				if ( ! empty( $collate ) )
-					$query .= $this->prepare( ' COLLATE %s', $collate );
-				mysql_query( $query, $dbh );
 			}
 		}
 	}