Description:
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ext/standard/html.c has incorrect mapping table which htmlentities() uses.

html.c is based on http://www.unicode.org/Public/MAPPINGS/OBSOLETE/UNI2SGML.TXT, but this mapping table is obsolete and not compatible with HTML4.0 or XHTML1.0. For example, U+2235(which is encoded to "\xe2\x88\xb5" with UTF-8) is not in http://www.w3.org/TR/xhtml1/DTD/xhtml-symbol.ent, but htmlentities() returns "∵".

U+226A(≪) and U+226B(≫) are similler case.

Reproduce code:
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<?php var_dump(htmlentities("\xe2\x88\xb5", ENT_QUOTES, "utf-8"));

Expected result:
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string(3) "??"

Actual result:
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string(8) "&becaus;"