update_core( string $from, string $to )

Upgrades the core of WordPress.


Description Description

This will create a .maintenance file at the base of the WordPress directory to ensure that people can not access the web site, when the files are being copied to their locations.

The files in the $_old_files list will be removed and the new files copied from the zip file after the database is upgraded.

The files in the $_new_bundled_files list will be added to the installation if the version is greater than or equal to the old version being upgraded.

The steps for the upgrader for after the new release is downloaded and unzipped is:

  1. Test unzipped location for select files to ensure that unzipped worked.
  2. Create the .maintenance file in current WordPress base.
  3. Copy new WordPress directory over old WordPress files.
  4. Upgrade WordPress to new version. 4.1. Copy all files/folders other than wp-content 4.2. Copy any language files to WP_LANG_DIR (which may differ from WP_CONTENT_DIR 4.3. Copy any new bundled themes/plugins to their respective locations
  5. Delete new WordPress directory path.
  6. Delete .maintenance file.
  7. Remove old files.
  8. Delete ‘update_core’ option.

There are several areas of failure. For instance if PHP times out before step 6, then you will not be able to access any portion of your site. Also, since the upgrade will not continue where it left off, you will not be able to automatically remove old files and remove the ‘update_core’ option. This isn’t that bad.

If the copy of the new WordPress over the old fails, then the worse is that the new WordPress directory will remain.

If it is assumed that every file will be copied over, including plugins and themes, then if you edit the default theme, you should rename it, so that your changes remain.


Parameters Parameters

$from

(string) (Required) New release unzipped path.

$to

(string) (Required) Path to old WordPress installation.


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Return Return

(WP_Error|null) WP_Error on failure, null on success.


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Source Source

File: wp-admin/includes/update-core.php

function update_core($from, $to) {
	global $wp_filesystem, $_old_files, $_new_bundled_files, $wpdb;

	@set_time_limit( 300 );

	/**
	 * Filters feedback messages displayed during the core update process.
	 *
	 * The filter is first evaluated after the zip file for the latest version
	 * has been downloaded and unzipped. It is evaluated five more times during
	 * the process:
	 *
	 * 1. Before WordPress begins the core upgrade process.
	 * 2. Before Maintenance Mode is enabled.
	 * 3. Before WordPress begins copying over the necessary files.
	 * 4. Before Maintenance Mode is disabled.
	 * 5. Before the database is upgraded.
	 *
	 * @since 2.5.0
	 *
	 * @param string $feedback The core update feedback messages.
	 */
	apply_filters( 'update_feedback', __( 'Verifying the unpacked files…' ) );

	// 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' ) ) {
			$distro = $root;
			break;
		}
	}
	if ( ! $distro ) {
		$wp_filesystem->delete( $from, true );
		return new WP_Error( 'insane_distro', __('The update could not be unpacked') );
	}


	/*
	 * Import $wp_version, $required_php_version, and $required_mysql_version from the new version.
	 * DO NOT globalise any variables imported from `version-current.php` in this function.
	 *
	 * 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' );
	}

	$wp_filesystem->chmod( $versions_file, FS_CHMOD_FILE );
	require( WP_CONTENT_DIR . '/upgrade/version-current.php' );
	$wp_filesystem->delete( $versions_file );

	$php_version    = phpversion();
	$mysql_version  = $wpdb->db_version();
	$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
		$mysql_compat = version_compare( $mysql_version, $required_mysql_version, '>=' );

	if ( !$mysql_compat || !$php_compat )
		$wp_filesystem->delete($from, true);

	if ( !$mysql_compat && !$php_compat )
		return new WP_Error( 'php_mysql_not_compatible', sprintf( __('The update cannot be installed because WordPress %1$s requires PHP version %2$s or higher and MySQL version %3$s or higher. You are running PHP version %4$s and MySQL version %5$s.'), $wp_version, $required_php_version, $required_mysql_version, $php_version, $mysql_version ) );
	elseif ( !$php_compat )
		return new WP_Error( 'php_not_compatible', sprintf( __('The update cannot be installed because WordPress %1$s requires PHP version %2$s or higher. You are running version %3$s.'), $wp_version, $required_php_version, $php_version ) );
	elseif ( !$mysql_compat )
		return new WP_Error( 'mysql_not_compatible', sprintf( __('The update cannot be installed because WordPress %1$s requires MySQL version %2$s or higher. You are running version %3$s.'), $wp_version, $required_mysql_version, $mysql_version ) );

	/** This filter is documented in wp-admin/includes/update-core.php */
	apply_filters( 'update_feedback', __( 'Preparing to install the latest version…' ) );

	// Don't copy wp-content, we'll deal with that below
	// We also copy version.php last so failed updates report their old version
	$skip = array( 'wp-content', 'wp-includes/version.php' );
	$check_is_writable = array();

	// Check to see which files don't really need updating - only available for 3.7 and higher
	if ( function_exists( 'get_core_checksums' ) ) {
		// Find the local version of the working directory
		$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' ) ) )
					continue;
				if ( md5_file( ABSPATH . $file ) === $checksum )
					$skip[] = $file;
				else
					$check_is_writable[ $file ] = ABSPATH . $file;
			}
		}
	}

	// 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 ] );
			}

			// Store package-relative paths (the key) of non-writable files in the WP_Error object.
			$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 ) );
		}
	}

	/** 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';
	$wp_filesystem->delete($maintenance_file);
	$wp_filesystem->put_contents($maintenance_file, $maintenance_string, FS_CHMOD_FILE);

	/** 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 ) ) );

	// 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' );
		}
		$wp_filesystem->chmod( $to . 'wp-includes/version.php', FS_CHMOD_FILE );
	}

	// 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' ) ) ) {
				$skip[] = $file;
				continue;
			}
			if ( file_exists( ABSPATH . $file ) && md5_file( ABSPATH . $file ) == $checksum )
				$skip[] = $file;
			else
				$failed[] = $file;
		}
	}

	// 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 );
		}

		// 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 ) ) );
		}
	}

	// 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) )
			$lang_dir = WP_LANG_DIR;
		else
			$lang_dir = WP_CONTENT_DIR . '/languages';

		if ( !@is_dir($lang_dir) && 0 === strpos($lang_dir, ABSPATH) ) { // Check the language directory exists first
			$wp_filesystem->mkdir($to . str_replace(ABSPATH, '', $lang_dir), FS_CHMOD_DIR); // If it's within the ABSPATH we can handle it here, otherwise they're out of luck.
			clearstatcache(); // for FTP, Need to clear the stat cache
		}

		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 ) ) );
			}
		}
	}

	/** 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.
	if ( '3.5' == $old_wp_version ) {
		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/' );
		}
	}

	// Copy New bundled plugins & themes
	// This gives us the ability to install new plugins & themes bundled with 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 ) ) {
		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, '>' ) ) {
				$directory = ('/' == $file[ strlen($file)-1 ]);
				list($type, $filename) = explode('/', $file, 2);

				// Check to see if the bundled items exist before attempting to copy them
				if ( ! $wp_filesystem->exists( $from . $distro . 'wp-content/' . $file ) )
					continue;

				if ( 'plugins' == $type )
					$dest = $wp_filesystem->wp_plugins_dir();
				elseif ( 'themes' == $type )
					$dest = trailingslashit($wp_filesystem->wp_themes_dir()); // Back-compat, ::wp_themes_dir() did not return trailingslash'd pre-3.2
				else
					continue;

				if ( ! $directory ) {
					if ( ! $development_build && $wp_filesystem->exists( $dest . $filename ) )
						continue;

					if ( ! $wp_filesystem->copy($from . $distro . 'wp-content/' . $file, $dest . $filename, FS_CHMOD_FILE) )
						$result = new WP_Error( "copy_failed_for_new_bundled_$type", __( 'Could not copy file.' ), $dest . $filename );
				} else {
					if ( ! $development_build && $wp_filesystem->is_dir( $dest . $filename ) )
						continue;

					$wp_filesystem->mkdir($dest . $filename, FS_CHMOD_DIR);
					$_result = copy_dir( $from . $distro . 'wp-content/' . $file, $dest . $filename);

					// If a error occurs partway through this final step, keep the error flowing through, but keep process going.
					if ( is_wp_error( $_result ) ) {
						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 ) ) );
					}
				}
			}
		} //end foreach
	}

	// 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;
		$wp_filesystem->delete($old_file, true);
	}

	// Remove any Genericons example.html's from the filesystem
	_upgrade_422_remove_genericons();

	// Remove the REST API plugin if its version is Beta 4 or lower
	_upgrade_440_force_deactivate_incompatible_plugins();

	// 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));

	// Clear the cache to prevent an update_option() from saving a stale db_version to the cache
	wp_cache_flush();
	// (Not all cache back ends listen to 'flush')
	wp_cache_delete( 'alloptions', 'options' );

	// Remove working directory
	$wp_filesystem->delete($from, true);

	// Force refresh of update information
	if ( function_exists('delete_site_transient') )
		delete_site_transient('update_core');
	else
		delete_option('update_core');

	/**
	 * Fires after WordPress core has been successfully updated.
	 *
	 * @since 3.3.0
	 *
	 * @param string $wp_version The current WordPress version.
	 */
	do_action( '_core_updated_successfully', $wp_version );

	// Clear the option that blocks auto updates after failures, now that we've been successful.
	if ( function_exists( 'delete_site_option' ) )
		delete_site_option( 'auto_core_update_failed' );

	return $wp_version;
}

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Changelog Changelog

Changelog
Version Description
2.7.0 Introduced.


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