Improve advanced cache file may be writable while directory may not

[8ctopus]

This pull request addresses an issue where the advanced-cache.php file is not created because WP_CONTENT_DIR is not writable by the PHP process.

The installation is based on Roots Bedrock. For security reasons, file ownership was set to ubuntu:ubuntu, and PHP runs as www-data. As a result of this architecture, the create_advanced_cache_file function returns false.

cache-enabler/inc/cache_enabler_disk.class.php

Lines 281 to 286 in efdae40

	public static function create_advanced_cache_file() {
	if ( ! is_writable( WP_CONTENT_DIR ) ) {
	return false;
	}

Here’s a snapshot of the directory structure:

la /srv/wordpress/web/app
total 20
drwxrwxr-x  5 ubuntu ubuntu 4096 May  5 13:57 .
drwxrwxr-x  4 ubuntu ubuntu 4096 May  5 07:29 ..
lrwxrwxrwx  1 ubuntu ubuntu   49 May  5 13:57 advanced-cache.php -> ../../../storage/cache-enabler/advanced-cache.php
lrwxrwxrwx  1 ubuntu ubuntu   14 Jul 17  2023 cache -> ../../../cache
drwxrwxr-x  3 ubuntu ubuntu 4096 Apr  6  2023 mu-plugins
drwxrwxr-x 11 ubuntu ubuntu 4096 May  5 07:35 plugins
drwxrwxr-x  4 ubuntu ubuntu 4096 Jul 10  2023 themes
lrwxrwxrwx  1 ubuntu ubuntu   19 Jul 17  2023 uploads -> ../../../wp-uploads

In this setup, WP_CONTENT_DIR itself isn't writable by www-data, but the actual advanced-cache.php file is writable thanks to the symlink pointing to a directory owned by www-data.

Removing the above code block should have no consequences as the return value of the file_put_contents function is checked later on.