diff --git a/src/wp-admin/includes/update-core.php b/src/wp-admin/includes/update-core.php
index 1f302cf4a4ff..37c2c287a4fe 100644
--- a/src/wp-admin/includes/update-core.php
+++ b/src/wp-admin/includes/update-core.php
@@ -924,14 +924,19 @@ function update_core( $from, $to ) {
 	// Sanity check the unzipped distribution.
 	$distro = '';
 	$roots  = array( '/wordpress/', '/wordpress-mu/' );
+
 	foreach ( $roots as $root ) {
-		if ( $wp_filesystem->exists( $from . $root . 'readme.html' ) && $wp_filesystem->exists( $from . $root . 'wp-includes/version.php' ) ) {
+		if ( $wp_filesystem->exists( $from . $root . 'readme.html' )
+			&& $wp_filesystem->exists( $from . $root . 'wp-includes/version.php' )
+		) {
 			$distro = $root;
 			break;
 		}
 	}
+
 	if ( ! $distro ) {
 		$wp_filesystem->delete( $from, true );
+
 		return new WP_Error( 'insane_distro', __( 'The update could not be unpacked' ) );
 	}
 
@@ -942,9 +947,15 @@ function update_core( $from, $to ) {
 	 * BC Note: $wp_filesystem->wp_content_dir() returned unslashed pre-2.8.
 	 */
 	$versions_file = trailingslashit( $wp_filesystem->wp_content_dir() ) . 'upgrade/version-current.php';
+
 	if ( ! $wp_filesystem->copy( $from . $distro . 'wp-includes/version.php', $versions_file ) ) {
 		$wp_filesystem->delete( $from, true );
-		return new WP_Error( 'copy_failed_for_version_file', __( 'The update cannot be installed because we will be unable to copy some files. This is usually due to inconsistent file permissions.' ), 'wp-includes/version.php' );
+
+		return new WP_Error(
+			'copy_failed_for_version_file',
+			__( 'The update cannot be installed because we will be unable to copy some files. This is usually due to inconsistent file permissions.' ),
+			'wp-includes/version.php'
+		);
 	}
 
 	$wp_filesystem->chmod( $versions_file, FS_CHMOD_FILE );
@@ -965,6 +976,7 @@ function update_core( $from, $to ) {
 	$old_wp_version    = $GLOBALS['wp_version']; // The version of WordPress we're updating from.
 	$development_build = ( false !== strpos( $old_wp_version . $wp_version, '-' ) ); // A dash in the version indicates a development release.
 	$php_compat        = version_compare( $php_version, $required_php_version, '>=' );
+
 	if ( file_exists( WP_CONTENT_DIR . '/db.php' ) && empty( $wpdb->is_mysql ) ) {
 		$mysql_compat = true;
 	} else {
@@ -1057,23 +1069,31 @@ function update_core( $from, $to ) {
 		$working_dir_local = WP_CONTENT_DIR . '/upgrade/' . basename( $from ) . $distro;
 
 		$checksums = get_core_checksums( $wp_version, isset( $wp_local_package ) ? $wp_local_package : 'en_US' );
+
 		if ( is_array( $checksums ) && isset( $checksums[ $wp_version ] ) ) {
 			$checksums = $checksums[ $wp_version ]; // Compat code for 3.7-beta2.
 		}
+
 		if ( is_array( $checksums ) ) {
 			foreach ( $checksums as $file => $checksum ) {
 				if ( 'wp-content' === substr( $file, 0, 10 ) ) {
 					continue;
 				}
+
 				if ( ! file_exists( ABSPATH . $file ) ) {
 					continue;
 				}
+
 				if ( ! file_exists( $working_dir_local . $file ) ) {
 					continue;
 				}
-				if ( '.' === dirname( $file ) && in_array( pathinfo( $file, PATHINFO_EXTENSION ), array( 'html', 'txt' ), true ) ) {
+
+				if ( '.' === dirname( $file )
+					&& in_array( pathinfo( $file, PATHINFO_EXTENSION ), array( 'html', 'txt' ), true )
+				) {
 					continue;
 				}
+
 				if ( md5_file( ABSPATH . $file ) === $checksum ) {
 					$skip[] = $file;
 				} else {
@@ -1086,11 +1106,14 @@ function update_core( $from, $to ) {
 	// If we're using the direct method, we can predict write failures that are due to permissions.
 	if ( $check_is_writable && 'direct' === $wp_filesystem->method ) {
 		$files_writable = array_filter( $check_is_writable, array( $wp_filesystem, 'is_writable' ) );
+
 		if ( $files_writable !== $check_is_writable ) {
 			$files_not_writable = array_diff_key( $check_is_writable, $files_writable );
+
 			foreach ( $files_not_writable as $relative_file_not_writable => $file_not_writable ) {
 				// If the writable check failed, chmod file to 0644 and try again, same as copy_dir().
 				$wp_filesystem->chmod( $file_not_writable, FS_CHMOD_FILE );
+
 				if ( $wp_filesystem->is_writable( $file_not_writable ) ) {
 					unset( $files_not_writable[ $relative_file_not_writable ] );
 				}
@@ -1100,13 +1123,18 @@ function update_core( $from, $to ) {
 			$error_data = version_compare( $old_wp_version, '3.7-beta2', '>' ) ? array_keys( $files_not_writable ) : '';
 
 			if ( $files_not_writable ) {
-				return new WP_Error( 'files_not_writable', __( 'The update cannot be installed because we will be unable to copy some files. This is usually due to inconsistent file permissions.' ), implode( ', ', $error_data ) );
+				return new WP_Error(
+					'files_not_writable',
+					__( 'The update cannot be installed because we will be unable to copy some files. This is usually due to inconsistent file permissions.' ),
+					implode( ', ', $error_data )
+				);
 			}
 		}
 	}
 
 	/** This filter is documented in wp-admin/includes/update-core.php */
 	apply_filters( 'update_feedback', __( 'Enabling Maintenance mode…' ) );
+
 	// Create maintenance file to signal that we are upgrading.
 	$maintenance_string = '<?php $upgrading = ' . time() . '; ?>';
 	$maintenance_file   = $to . '.maintenance';
@@ -1115,18 +1143,29 @@ function update_core( $from, $to ) {
 
 	/** This filter is documented in wp-admin/includes/update-core.php */
 	apply_filters( 'update_feedback', __( 'Copying the required files&#8230;' ) );
+
 	// Copy new versions of WP files into place.
 	$result = _copy_dir( $from . $distro, $to, $skip );
+
 	if ( is_wp_error( $result ) ) {
-		$result = new WP_Error( $result->get_error_code(), $result->get_error_message(), substr( $result->get_error_data(), strlen( $to ) ) );
+		$result = new WP_Error(
+			$result->get_error_code(),
+			$result->get_error_message(),
+			substr( $result->get_error_data(), strlen( $to ) )
+		);
 	}
 
 	// Since we know the core files have copied over, we can now copy the version file.
 	if ( ! is_wp_error( $result ) ) {
 		if ( ! $wp_filesystem->copy( $from . $distro . 'wp-includes/version.php', $to . 'wp-includes/version.php', true /* overwrite */ ) ) {
 			$wp_filesystem->delete( $from, true );
-			$result = new WP_Error( 'copy_failed_for_version_file', __( 'The update cannot be installed because we will be unable to copy some files. This is usually due to inconsistent file permissions.' ), 'wp-includes/version.php' );
+			$result = new WP_Error(
+				'copy_failed_for_version_file',
+				__( 'The update cannot be installed because we will be unable to copy some files. This is usually due to inconsistent file permissions.' ),
+				'wp-includes/version.php'
+			);
 		}
+
 		$wp_filesystem->chmod( $to . 'wp-includes/version.php', FS_CHMOD_FILE );
 
 		/*
@@ -1141,19 +1180,25 @@ function update_core( $from, $to ) {
 	// Check to make sure everything copied correctly, ignoring the contents of wp-content.
 	$skip   = array( 'wp-content' );
 	$failed = array();
+
 	if ( isset( $checksums ) && is_array( $checksums ) ) {
 		foreach ( $checksums as $file => $checksum ) {
 			if ( 'wp-content' === substr( $file, 0, 10 ) ) {
 				continue;
 			}
+
 			if ( ! file_exists( $working_dir_local . $file ) ) {
 				continue;
 			}
-			if ( '.' === dirname( $file ) && in_array( pathinfo( $file, PATHINFO_EXTENSION ), array( 'html', 'txt' ), true ) ) {
+
+			if ( '.' === dirname( $file )
+				&& in_array( pathinfo( $file, PATHINFO_EXTENSION ), array( 'html', 'txt' ), true )
+			) {
 				$skip[] = $file;
 				continue;
 			}
-			if ( file_exists( ABSPATH . $file ) && md5_file( ABSPATH . $file ) == $checksum ) {
+
+			if ( file_exists( ABSPATH . $file ) && md5_file( ABSPATH . $file ) === $checksum ) {
 				$skip[] = $file;
 			} else {
 				$failed[] = $file;
@@ -1164,6 +1209,7 @@ function update_core( $from, $to ) {
 	// Some files didn't copy properly.
 	if ( ! empty( $failed ) ) {
 		$total_size = 0;
+
 		foreach ( $failed as $file ) {
 			if ( file_exists( $working_dir_local . $file ) ) {
 				$total_size += filesize( $working_dir_local . $file );
@@ -1173,12 +1219,18 @@ function update_core( $from, $to ) {
 		// If we don't have enough free space, it isn't worth trying again.
 		// Unlikely to be hit due to the check in unzip_file().
 		$available_space = @disk_free_space( ABSPATH );
+
 		if ( $available_space && $total_size >= $available_space ) {
 			$result = new WP_Error( 'disk_full', __( 'There is not enough free disk space to complete the update.' ) );
 		} else {
 			$result = _copy_dir( $from . $distro, $to, $skip );
+
 			if ( is_wp_error( $result ) ) {
-				$result = new WP_Error( $result->get_error_code() . '_retry', $result->get_error_message(), substr( $result->get_error_data(), strlen( $to ) ) );
+				$result = new WP_Error(
+					$result->get_error_code() . '_retry',
+					$result->get_error_message(),
+					substr( $result->get_error_data(), strlen( $to ) )
+				);
 			}
 		}
 	}
@@ -1186,7 +1238,7 @@ function update_core( $from, $to ) {
 	// Custom content directory needs updating now.
 	// Copy languages.
 	if ( ! is_wp_error( $result ) && $wp_filesystem->is_dir( $from . $distro . 'wp-content/languages' ) ) {
-		if ( WP_LANG_DIR != ABSPATH . WPINC . '/languages' || @is_dir( WP_LANG_DIR ) ) {
+		if ( WP_LANG_DIR !== ABSPATH . WPINC . '/languages' || @is_dir( WP_LANG_DIR ) ) {
 			$lang_dir = WP_LANG_DIR;
 		} else {
 			$lang_dir = WP_CONTENT_DIR . '/languages';
@@ -1201,10 +1253,16 @@ function update_core( $from, $to ) {
 
 		if ( @is_dir( $lang_dir ) ) {
 			$wp_lang_dir = $wp_filesystem->find_folder( $lang_dir );
+
 			if ( $wp_lang_dir ) {
 				$result = copy_dir( $from . $distro . 'wp-content/languages/', $wp_lang_dir );
+
 				if ( is_wp_error( $result ) ) {
-					$result = new WP_Error( $result->get_error_code() . '_languages', $result->get_error_message(), substr( $result->get_error_data(), strlen( $wp_lang_dir ) ) );
+					$result = new WP_Error(
+						$result->get_error_code() . '_languages',
+						$result->get_error_message(),
+						substr( $result->get_error_data(), strlen( $wp_lang_dir ) )
+					);
 				}
 			}
 		}
@@ -1212,12 +1270,16 @@ function update_core( $from, $to ) {
 
 	/** This filter is documented in wp-admin/includes/update-core.php */
 	apply_filters( 'update_feedback', __( 'Disabling Maintenance mode&#8230;' ) );
+
 	// Remove maintenance file, we're done with potential site-breaking changes.
 	$wp_filesystem->delete( $maintenance_file );
 
-	// 3.5 -> 3.5+ - an empty twentytwelve directory was created upon upgrade to 3.5 for some users, preventing installation of Twenty Twelve.
+	// 3.5 -> 3.5+ - an empty twentytwelve directory was created upon upgrade to 3.5 for some users,
+	// preventing installation of Twenty Twelve.
 	if ( '3.5' === $old_wp_version ) {
-		if ( is_dir( WP_CONTENT_DIR . '/themes/twentytwelve' ) && ! file_exists( WP_CONTENT_DIR . '/themes/twentytwelve/style.css' ) ) {
+		if ( is_dir( WP_CONTENT_DIR . '/themes/twentytwelve' )
+			&& ! file_exists( WP_CONTENT_DIR . '/themes/twentytwelve/style.css' )
+		) {
 			$wp_filesystem->delete( $wp_filesystem->wp_themes_dir() . 'twentytwelve/' );
 		}
 	}
@@ -1228,7 +1290,9 @@ function update_core( $from, $to ) {
 	 * future versions of WordPress whilst avoiding the re-install upon upgrade issue.
 	 * $development_build controls us overwriting bundled themes and plugins when a non-stable release is being updated.
 	 */
-	if ( ! is_wp_error( $result ) && ( ! defined( 'CORE_UPGRADE_SKIP_NEW_BUNDLED' ) || ! CORE_UPGRADE_SKIP_NEW_BUNDLED ) ) {
+	if ( ! is_wp_error( $result )
+		&& ( ! defined( 'CORE_UPGRADE_SKIP_NEW_BUNDLED' ) || ! CORE_UPGRADE_SKIP_NEW_BUNDLED )
+	) {
 		foreach ( (array) $_new_bundled_files as $file => $introduced_version ) {
 			// If a $development_build or if $introduced version is greater than what the site was previously running.
 			if ( $development_build || version_compare( $introduced_version, $old_wp_version, '>' ) ) {
@@ -1271,7 +1335,12 @@ function update_core( $from, $to ) {
 						if ( ! is_wp_error( $result ) ) {
 							$result = new WP_Error;
 						}
-						$result->add( $_result->get_error_code() . "_$type", $_result->get_error_message(), substr( $_result->get_error_data(), strlen( $dest ) ) );
+
+						$result->add(
+							$_result->get_error_code() . "_$type",
+							$_result->get_error_message(),
+							substr( $_result->get_error_data(), strlen( $dest ) )
+						);
 					}
 				}
 			}
@@ -1281,12 +1350,14 @@ function update_core( $from, $to ) {
 	// Handle $result error from the above blocks.
 	if ( is_wp_error( $result ) ) {
 		$wp_filesystem->delete( $from, true );
+
 		return $result;
 	}
 
 	// Remove old files.
 	foreach ( $_old_files as $old_file ) {
 		$old_file = $to . $old_file;
+
 		if ( ! $wp_filesystem->exists( $old_file ) ) {
 			continue;
 		}
@@ -1306,6 +1377,7 @@ function update_core( $from, $to ) {
 	// Upgrade DB with separate request.
 	/** This filter is documented in wp-admin/includes/update-core.php */
 	apply_filters( 'update_feedback', __( 'Upgrading database&#8230;' ) );
+
 	$db_upgrade_url = admin_url( 'upgrade.php?step=upgrade_db' );
 	wp_remote_post( $db_upgrade_url, array( 'timeout' => 60 ) );
 
@@ -1387,6 +1459,7 @@ function _copy_dir( $from, $to, $skip_list = array() ) {
 			if ( ! $wp_filesystem->copy( $from . $filename, $to . $filename, true, FS_CHMOD_FILE ) ) {
 				// If copy failed, chmod file to 0644 and try again.
 				$wp_filesystem->chmod( $to . $filename, FS_CHMOD_FILE );
+
 				if ( ! $wp_filesystem->copy( $from . $filename, $to . $filename, true, FS_CHMOD_FILE ) ) {
 					return new WP_Error( 'copy_failed__copy_dir', __( 'Could not copy file.' ), $to . $filename );
 				}
@@ -1411,6 +1484,7 @@ function _copy_dir( $from, $to, $skip_list = array() ) {
 			 * of the existing $skip_list.
 			 */
 			$sub_skip_list = array();
+
 			foreach ( $skip_list as $skip_item ) {
 				if ( 0 === strpos( $skip_item, $filename . '/' ) ) {
 					$sub_skip_list[] = preg_replace( '!^' . preg_quote( $filename, '!' ) . '/!i', '', $skip_item );
@@ -1418,11 +1492,13 @@ function _copy_dir( $from, $to, $skip_list = array() ) {
 			}
 
 			$result = _copy_dir( $from . $filename, $to . $filename, $sub_skip_list );
+
 			if ( is_wp_error( $result ) ) {
 				return $result;
 			}
 		}
 	}
+
 	return true;
 }
 
@@ -1516,6 +1592,7 @@ function _upgrade_422_remove_genericons() {
 
 	foreach ( $affected_files as $file ) {
 		$gen_dir = $wp_filesystem->find_folder( trailingslashit( dirname( $file ) ) );
+
 		if ( empty( $gen_dir ) ) {
 			continue;
 		}
@@ -1546,11 +1623,14 @@ function _upgrade_422_find_genericons_files_in_folder( $directory ) {
 	$directory = trailingslashit( $directory );
 	$files     = array();
 
-	if ( file_exists( "{$directory}example.html" ) && false !== strpos( file_get_contents( "{$directory}example.html" ), '<title>Genericons</title>' ) ) {
+	if ( file_exists( "{$directory}example.html" )
+		&& false !== strpos( file_get_contents( "{$directory}example.html" ), '<title>Genericons</title>' )
+	) {
 		$files[] = "{$directory}example.html";
 	}
 
 	$dirs = glob( $directory . '*', GLOB_ONLYDIR );
+
 	if ( $dirs ) {
 		foreach ( $dirs as $dir ) {
 			$files = array_merge( $files, _upgrade_422_find_genericons_files_in_folder( $dir ) );