Deprecation Notices & Wasted CPU

My debug log is filled with deprecated notices when running this plugin on PHP 8.1:

[25-Jul-2023 14:49:01 UTC] PHP Deprecated:  preg_match(): Passing null to parameter #2 ($subject) of type string is deprecated in wp-content/plugins/woo-photo-reviews/includes/mobile_detect.php on line 1155
[25-Jul-2023 14:49:01 UTC] PHP Deprecated:  preg_match(): Passing null to parameter #2 ($subject) of type string is deprecated in wp-content/plugins/woo-photo-reviews/includes/mobile_detect.php on line 1155
[25-Jul-2023 14:49:01 UTC] PHP Deprecated:  preg_match(): Passing null to parameter #2 ($subject) of type string is deprecated in wp-content/plugins/woo-photo-reviews/includes/mobile_detect.php on line 1155
[25-Jul-2023 14:49:01 UTC] PHP Deprecated:  preg_match(): Passing null to parameter #2 ($subject) of type string is deprecated in wp-content/plugins/woo-photo-reviews/includes/mobile_detect.php on line 1155
[25-Jul-2023 14:49:01 UTC] PHP Deprecated:  preg_match(): Passing null to parameter #2 ($subject) of type string is deprecated in wp-content/plugins/woo-photo-reviews/includes/mobile_detect.php on line 1155
[25-Jul-2023 14:49:01 UTC] PHP Deprecated:  preg_match(): Passing null to parameter #2 ($subject) of type string is deprecated in wp-content/plugins/woo-photo-reviews/includes/mobile_detect.php on line 1155
[25-Jul-2023 14:49:01 UTC] PHP Deprecated:  preg_match(): Passing null to parameter #2 ($subject) of type string is deprecated in wp-content/plugins/woo-photo-reviews/includes/mobile_detect.php on line 1155
[25-Jul-2023 14:49:01 UTC] PHP Deprecated:  preg_match(): Passing null to parameter #2 ($subject) of type string is deprecated in wp-content/plugins/woo-photo-reviews/includes/mobile_detect.php on line 1155
[25-Jul-2023 14:49:01 UTC] PHP Deprecated:  preg_match(): Passing null to parameter #2 ($subject) of type string is deprecated in wp-content/plugins/woo-photo-reviews/includes/mobile_detect.php on line 1155
[25-Jul-2023 14:49:01 UTC] PHP Deprecated:  preg_match(): Passing null to parameter #2 ($subject) of type string is deprecated in wp-content/plugins/woo-photo-reviews/includes/mobile_detect.php on line 1155
[25-Jul-2023 14:49:01 UTC] PHP Deprecated:  preg_match(): Passing null to parameter #2 ($subject) of type string is deprecated in wp-content/plugins/woo-photo-reviews/includes/mobile_detect.php on line 1155
[25-Jul-2023 14:49:01 UTC] PHP Deprecated:  preg_match(): Passing null to parameter #2 ($subject) of type string is deprecated in wp-content/plugins/woo-photo-reviews/includes/mobile_detect.php on line 1155
[25-Jul-2023 14:49:01 UTC] PHP Deprecated:  preg_match(): Passing null to parameter #2 ($subject) of type string is deprecated in wp-content/plugins/woo-photo-reviews/includes/mobile_detect.php on line 1155
[25-Jul-2023 14:49:01 UTC] PHP Deprecated:  preg_match(): Passing null to parameter #2 ($subject) of type string is deprecated in wp-content/plugins/woo-photo-reviews/includes/mobile_detect.php on line 1155
[25-Jul-2023 14:49:01 UTC] PHP Deprecated:  preg_match(): Passing null to parameter #2 ($subject) of type string is deprecated in wp-content/plugins/woo-photo-reviews/includes/mobile_detect.php on line 1155
[25-Jul-2023 14:49:01 UTC] PHP Deprecated:  preg_match(): Passing null to parameter #2 ($subject) of type string is deprecated in wp-content/plugins/woo-photo-reviews/includes/mobile_detect.php on line 1155
[25-Jul-2023 14:49:01 UTC] PHP Deprecated:  preg_match(): Passing null to parameter #2 ($subject) of type string is deprecated in wp-content/plugins/woo-photo-reviews/includes/mobile_detect.php on line 1155
[25-Jul-2023 14:49:01 UTC] PHP Deprecated:  preg_match(): Passing null to parameter #2 ($subject) of type string is deprecated in wp-content/plugins/woo-photo-reviews/includes/mobile_detect.php on line 1155
[25-Jul-2023 14:49:01 UTC] PHP Deprecated:  preg_match(): Passing null to parameter #2 ($subject) of type string is deprecated in wp-content/plugins/woo-photo-reviews/includes/mobile_detect.php on line 1155
[25-Jul-2023 14:49:01 UTC] PHP Deprecated:  preg_match(): Passing null to parameter #2 ($subject) of type string is deprecated in wp-content/plugins/woo-photo-reviews/includes/mobile_detect.php on line 1155
[25-Jul-2023 14:49:01 UTC] PHP Deprecated:  preg_match(): Passing null to parameter #2 ($subject) of type string is deprecated in wp-content/plugins/woo-photo-reviews/includes/mobile_detect.php on line 1155
[25-Jul-2023 14:49:01 UTC] PHP Deprecated:  preg_match(): Passing null to parameter #2 ($subject) of type string is deprecated in wp-content/plugins/woo-photo-reviews/includes/mobile_detect.php on line 1155
[25-Jul-2023 14:49:01 UTC] PHP Deprecated:  preg_match(): Passing null to parameter #2 ($subject) of type string is deprecated in wp-content/plugins/woo-photo-reviews/includes/mobile_detect.php on line 1155
[25-Jul-2023 14:49:01 UTC] PHP Deprecated:  preg_match(): Passing null to parameter #2 ($subject) of type string is deprecated in wp-content/plugins/woo-photo-reviews/includes/mobile_detect.php on line 1155
[25-Jul-2023 14:49:01 UTC] PHP Deprecated:  preg_match(): Passing null to parameter #2 ($subject) of type string is deprecated in wp-content/plugins/woo-photo-reviews/includes/mobile_detect.php on line 1155
[25-Jul-2023 14:49:01 UTC] PHP Deprecated:  preg_match(): Passing null to parameter #2 ($subject) of type string is deprecated in wp-content/plugins/woo-photo-reviews/includes/mobile_detect.php on line 1155
[25-Jul-2023 14:49:01 UTC] PHP Deprecated:  preg_match(): Passing null to parameter #2 ($subject) of type string is deprecated in wp-content/plugins/woo-photo-reviews/includes/mobile_detect.php on line 1155
[25-Jul-2023 14:49:01 UTC] PHP Deprecated:  preg_match(): Passing null to parameter #2 ($subject) of type string is deprecated in wp-content/plugins/woo-photo-reviews/includes/mobile_detect.php on line 1155
[25-Jul-2023 14:49:01 UTC] PHP Deprecated:  preg_match(): Passing null to parameter #2 ($subject) of type string is deprecated in wp-content/plugins/woo-photo-reviews/includes/mobile_detect.php on line 1155
[25-Jul-2023 14:49:01 UTC] PHP Deprecated:  preg_match(): Passing null to parameter #2 ($subject) of type string is deprecated in wp-content/plugins/woo-photo-reviews/includes/mobile_detect.php on line 1155

I patched the function in question as follows:

		/**
		 * Some detection rules are relative (not standard),
		 * because of the diversity of devices, vendors and
		 * their conventions in representing the User-Agent or
		 * the HTTP headers.
		 *
		 * This method will be used to check custom regexes against
		 * the User-Agent string.
		 *
		 * @param string $regex
		 * @param string|null $userAgent
		 *
		 * @return bool
		 *
		 * @todo: search in the HTTP headers too.
		 */
		public function match($regex, $userAgent = null) {
			// Ensure that $userAgent is a non-null string.
			$userAgent = is_string($userAgent) ? $userAgent : '';

			$match = (bool) preg_match(sprintf('#%s#is', $regex), $userAgent, $matches);

			// If positive match is found, store the results for debug.
			if ($match) {
				$this->matchingRegex = $regex;
				$this->matchesArray  = $matches;
			}

			return $match;
		}

But the question still remains… why is this function being called on every single page load, even those that are not displaying or collecting photo reviews? That’s a real waste of CPU cycles.