3v4l.org

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<?php mb_substitute_character(0xfffd); var_dump(bin2hex(mb_convert_encoding("A\xfd\xbf\xbf\xbf\xbf\xbfB", 'UTF-16', 'UTF-8')));
Output for 5.4.0 - 5.4.45, 5.5.0 - 5.5.38, 5.6.0 - 5.6.28, 7.0.0 - 7.0.20, 7.1.0 - 7.1.10, 7.2.0 - 7.2.33, 7.3.12 - 7.3.33, 7.4.0 - 7.4.33, 8.0.0 - 8.0.30, 8.1.0 - 8.1.28, 8.2.0 - 8.2.18, 8.3.0 - 8.3.6
string(32) "0041fffdfffdfffdfffdfffdfffd0042"
Output for 5.3.0 - 5.3.29
string(8) "00410042"
Output for 4.3.0 - 4.3.11, 4.4.0 - 4.4.9, 5.0.0 - 5.0.5, 5.1.0 - 5.1.6, 5.2.0 - 5.2.17
string(12) "0041fffd0042"

preferences:
241.13 ms | 402 KiB | 353 Q