Fatal errror after updating to 4.7

We have found out that WordPress wouldn’t work with PHP7. When we downgrade to PHP5.6 it works without any problem….

A very bad thing! 🙁

Yeah that’s nice. Give the template or plugins debt. But all websites were before the update to 4.7 running on PHP7 without any problems. And after the update no longer.
And also some websites use the default template twenty twelve and no additional plugins. And this doesn’t work also.

If you’re going to update with PHP5.6 and after the update back to PHP7 works at some sites. So there is something on 4.7 what isn’t compatible whit PHP7. And this isn’t the first time this happens 🙁

For test I have installed a fresh installation. With no additional plugins and no caching. And it still is not working on PHP7. When I change I it to PHP5.6 it is working perfect. And when I change it back after the update to PHP7 the website is working without any problems. So something code what is used for the update is not working correctly with PHP7.

But this is not working for all sites. Some sites won’t work anymore on PHP7 after the update. The strange thing is that they work before the update without any problems on PHP7.

The same site give every time the same error. But each site give another error. But this is maybe possible that it are different templates.

Sorry, I don’t know exactly what you mean. On the load.php I have the following code where is_wp_error is defined.

function wp_set_wpdb_vars() {
	global $wpdb, $table_prefix;
	if ( !empty( $wpdb->error ) )
		dead_db();

	$wpdb->field_types = array( 'post_author' => '%d', 'post_parent' => '%d', 'menu_order' => '%d', 'term_id' => '%d', 'term_group' => '%d', 'term_taxonomy_id' => '%d',
		'parent' => '%d', 'count' => '%d','object_id' => '%d', 'term_order' => '%d', 'ID' => '%d', 'comment_ID' => '%d', 'comment_post_ID' => '%d', 'comment_parent' => '%d',
		'user_id' => '%d', 'link_id' => '%d', 'link_owner' => '%d', 'link_rating' => '%d', 'option_id' => '%d', 'blog_id' => '%d', 'meta_id' => '%d', 'post_id' => '%d',
		'user_status' => '%d', 'umeta_id' => '%d', 'comment_karma' => '%d', 'comment_count' => '%d',
		// multisite:
		'active' => '%d', 'cat_id' => '%d', 'deleted' => '%d', 'lang_id' => '%d', 'mature' => '%d', 'public' => '%d', 'site_id' => '%d', 'spam' => '%d',
	);

	$prefix = $wpdb->set_prefix( $table_prefix );

	if ( is_wp_error( $prefix ) ) {
		wp_load_translations_early();
		wp_die(
			/* translators: 1: $table_prefix 2: wp-config.php */
			sprintf( __( '<strong>ERROR</strong>: %1$s in %2$s can only contain numbers, letters, and underscores.' ),
				'<code>$table_prefix</code>',
				'<code>wp-config.php</code>'
			)
		);
	}
}

You mean this.

/**
 * Check whether variable is a WordPress Error.
 *
 * Returns true if $thing is an object of the WP_Error class.
 *
 * @since 2.1.0
 *
 * @param mixed $thing Check if unknown variable is a WP_Error object.
 * @return bool True, if WP_Error. False, if not WP_Error.
 */
function is_wp_error( $thing ) {
	return ( $thing instanceof WP_Error );
}