Fatal error in method advanced_robots_combine – foreach() receiving string inste

Issue Details
We are facing an error on the website [Website URL] related to the Rank Math SEO plugin version 2.5. The error is being recorded by Sentry and is affecting the proper loading of pages in certain cases.

Specific Error
pgsql
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Warning: foreach() argument must be of type array|object, string given
Stack Trace
The error occurs in the file /wp-content/plugins/seo-by-rank-math/includes/frontend/paper/class-paper.php on line 526, specifically inside the RankMath\Paper\Paper::advanced_robots_combine function.

The full call stack is:

RankMath\Paper\Paper::advanced_robots_combine (line 526)

RankMath\Paper\Singular::get_post_advanced_robots (line 219)

RankMath\Paper\Singular::advanced_robots (line 65)

RankMath\Paper\Paper::advanced_robots (line 275)

RankMath\Paper\Paper::get_robots (line 229)

RankMath\Frontend\Head::robots (line 220)

How to Reproduce
The issue occurs when:

A user accesses the website via a mobile device (case identified: iPhone with iOS 9.1 and Mobile Safari 9.0)

WP Rocket is performing page preload

The specific URL being accessed: https://www.donacoelha.com/meuapartamentinho/

Technical Analysis
In the advanced_robots_combine function, there is a foreach loop trying to iterate over the $advanced_robots variable:

php
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foreach ($advanced_robots as $key => $data) {
The issue happens because $advanced_robots is coming as a string instead of an array/object. Specifically, this occurs when Post::get_meta(‘advanced_robots’, $this->object->ID) returns a string instead of an array.

Environment
WordPress: 6.8

PHP: 8.1.32

Rank Math SEO: 2.5

Server: Linux 5.10.0-31-amd64

Theme: Flatsome

Other relevant plugins: WP Rocket

Suggested Solution
We recommend adding a type check before the foreach loop in the advanced_robots_combine function:

php
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// Line 526 in class-paper.php
if (!is_array($advanced_robots) && !is_object($advanced_robots)) {
return [];
}

foreach ($advanced_robots as $key => $data) {
// existing code…
}
This verification would ensure the function does not attempt to iterate over a string, which is causing the current error.

Additional Questions
Has this issue been identified and addressed in any newer versions of the plugin?

Are there any known incompatibilities between Rank Math SEO and WP Rocket during mobile preload?

Is there any specific configuration that could be causing this behavior?

Thank you in advance for your attention and support. I am available to provide any additional information if needed.