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About failures: https://kinsta.com/blog/10-things-not-to-do-in-php-7
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Cutting a string value using substr() can crash inside a character of several bytes. Functions named like mb_substr() can handle a character of several bytes.
Note: ‘Multibyte character set’ is not a proper name for in fact multibyte encoding.
This MySQL database does not cut off longer values anymore. Using a state-of-the-art version, your application can raise bugs.
HTML using F12:
Statements get outdated in a process of deprecation. My suggestion is to warn your application supplier in order to fix before a warning in yellow becomes an error in red.