Add examples for mb_scrub() - #5811
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The page had no example, which made it hard to see that the replacement happens in the string itself: terminals, browsers and fonts render an ill-formed byte sequence with a replacement character of their own, so visual output alone is misleading. Both examples use bin2hex() or var_dump() so the reader sees the bytes rather than the rendering. The first example also shows that the result depends on the substitute character: mbstring.substitute_character defaults to "?" (0x3F), so the scrubbed string is 41 3f 42, and 41 ef bf bd 42 only after calling mb_substitute_character(0xFFFD). The second example shows the practical use: a PCRE pattern with the u modifier fails on the raw input and succeeds once it has been scrubbed. A see also section is added, since the page had none and the substitute character is a prerequisite for reading the first example. Outputs verified on PHP 8.1, 8.4 and 8.5. Fixes: php#5562
jordikroon
reviewed
Aug 27, 2026
jordikroon
reviewed
Aug 27, 2026
This was referenced Aug 31, 2026
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The
mb_scrub()page had no example, which made it hard to see that the replacement happens in the string itself. Terminals, browsers and fonts render an ill-formed byte sequence with a replacement character of their own, so visual output alone is misleading. Both examples therefore usebin2hex()orvar_dump(), so the reader sees the bytes rather than the rendering.Byte-level replacement. The first example also shows that the result depends on the substitute character.
mbstring.substitute_characterdefaults to"?"(0x3F), so scrubbing"A\xFFB"yields41 3f 42;41 ef bf bd 42is only produced after callingmb_substitute_character(0xFFFD). This differs from the output given in the issue, which assumed U+FFFD by default.Use before UTF-8 aware processing. The second example shows the practical case: a PCRE pattern with the
umodifier fails on the raw input withMalformed UTF-8 characters, possibly incorrectly encoded, and succeeds once the string has been scrubbed.A see also section is added, since the page had none and the substitute character is a prerequisite for reading the first example.
Both
<screen>blocks were extracted from the file and compared byte for byte against the real output on PHP 8.1, 8.4 and 8.5.Fixes: #5562