Avoid incidental execution of system report unless it has not been executed in a week

[diosmosis]

Description:

Fixes #893

Changes:

• Look for PHP binary in system report only on demand.
• Cache whether errors exist in the system report for use with the admin menu item and notification. Before starting this check, assume there are no errors, so if the system report fails, Matomo for WordPress will still be accessible.

Review

• Functional review done
• Potential edge cases thought about (behavior of the code with strange input, with strange internal state or possible interactions with other Matomo subsystems)
• Usability review done (is anything maybe unclear or think about anything that would cause people to reach out to support)
• Security review done
• Wording review done
• Code review done
• Tests were added if useful/possible
• Reviewed for breaking changes
• Developer changelog updated if needed
• Documentation added if needed
• Existing documentation updated if needed

[tsteur]

@diosmosis great find! This would slow down things a lot executing system check every time.

I wonder if it's avoidable to call this every time in the first place but until then a cache will do 👍 I do wonder if it makes sense to use transients for caching? https://www.godaddy.com/resources/skills/transient-date-wordpress I don't know the pros/cons though. Maybe just something to consider. I believe when you then eg invalidate transients, then our cache will be also invalidated I believe which may be helpful at certain times. There could be cons too.

Off topic:
There is below string that is not really translatable into other languages. Any chance we can utilise %s there and put it in one sentence? Or we could create a separate issue for it and tackle it another time. Depending on the language, you can't translate 3 sentence parts individually.

<p>' . esc_html__( 'There are some errors in the', 'matomo' ) .
					' <a href="' . esc_url( admin_url( 'admin.php?page=matomo-systemreport' ) ) . '">' . esc_html__( 'Matomo Diagnostics System report', 'matomo' ) . '</a> ' .
					esc_html__( 'that may prevent the plugin for working normally.', 'matomo' ) . '</p></div>';

[diosmosis]

Transients were what I was looking for 👍, I checked the object cache but the docs stated it would not always persist past a single request so I didn't use it.