Description:

When generating the tables for PDF reports we are truncating the row values after a certain amount of chars (55). If a string contained a multibyte character (umlauts, emojis, ...) around this position, it happened, that the multibyte sequence was disrupted.

This did cause any bigger issues on PHP 7, where only parts of the string were displayed in the PDF
On PHP 8 this produced an error, causing an abort of the PDF generation.

Simply using mb_substr instead of substr fixes this issue for me.

If someone wants to reproduce:

• Track any type of content (action, site search keyword, ...) with something like öööööööööööööööööööööööööööööööööööööööööööööööööööööööööööö
• Create a PDF report that contains this content type
• Click the download button to directly generate the report

@tsteur I've targeted next_release as it's really a minimal, low-risk change

fixes #18499

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