Description:
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I don't know if this is related/the real bug.
https://bugs.php.net/bug.php?id=70072

After reading this https://github.com/php/php-src/blob/php-7.3.0RC2/UPGRADING

I noticed that example
mb_strtoupper("Straße")
// Produces STRAßE on PHP 7.2
// Produces STRASSE on PHP 7.3

But why are we doing this? There is an https://www.fileformat.info/info/unicode/char/1e9e/index.htm in UTF-8 spec and there for no need for a casing mapping!

Expected result:
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mb_strtoupper("Straße")

should give a STRAßE with an LATIN CAPITAL LETTER SHARP S

Actual result:
--------------
STRAßE with an LATIN SMALL LETTER SHARP S