Description:
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I am conducted some tests on idn_to_ascii and idn_to_utf8 methods from intl extension. See the test script example for $flags.

Those 2 methods are mainly used for domain names conversion and therefore should comply with IDNA 2008 (RFC 5891) and not only UTS#46.
During my tests, the following input domains were considered valid by idn_to_ascii while they contain DISALLOWED character in IDNA 2008:
 - ????????????????????????????????.????????????
 - 〈普遍接受-测试.世界
 - Ė.ua-test.top

See https://util.unicode.org/UnicodeJsps/idna.jsp?a=%F0%90%8D%81%F0%90%8D%83%F0%90%8C%B9%F0%90%8C%BF%F0%90%8D%88%F0%90%8C%B3%F0%90%8C%B5%F0%90%8C%BF.%F0%90%8C%B2%F0%90%8D%88%F0%90%8C%BC%0D%0A%E3%80%88%E6%99%AE%E9%81%8D%E6%8E%A5%E5%8F%97-%E6%B5%8B%E8%AF%95.%E4%B8%96%E7%95%8C%0D%0A%C4%96.ua-test.top

Test script:
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$result = idn_to_ascii($input,
    IDNA_DEFAULT
    | IDNA_USE_STD3_RULES
    | IDNA_CHECK_BIDI
    | IDNA_CHECK_CONTEXTJ
    | IDNA_NONTRANSITIONAL_TO_ASCII,
    INTL_IDNA_VARIANT_UTS46, $idnaInfo);
echo $result;

Expected result:
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idn_to_ascii whould return null and $idn_info should contain error IDNA_ERROR_DISALLOWED with those domains:
 - ????????????????????????????????.????????????
 - 〈普遍接受-测试.世界
 - Ė.ua-test.top

Actual result:
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idn_to_ascii converts those domains to A-label without error.