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rfc:inconsistent-behaviors [2014/02/05 03:16] yohgakirfc:inconsistent-behaviors [2017/09/22 13:28] – external edit
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 Type juggling only works for INTEGER or HEX like strings. Type juggling only works for INTEGER or HEX like strings.
 +Most problematic is HEX like strings being auto-coerced during
 +comparison, but using //different rules// from manual casting. That
 +is, ( 0x0A == "0x0A" ) is not treated as ( 0x0A == (int)"0x0A" ),
 +although "0x0A" //is// translated to a number.
 +This despite http://us2.php.net/manual/en/language.operators.comparison.php, which
 +states clearly that for number-string comparison, we "Translate
 +strings and resources to numbers." While it is feasible that some
 +string patterns cannot be "translated" (OCTAL and BINARY) at all, once
 +a "translation" is attempted, it should follow the same rules as (int)
 +casting for the same string. It is hard to view it is anything but a
 +bug that it does not.
 === HEX === === HEX ===
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 https://bugs.php.net/bug.php?id=66211 https://bugs.php.net/bug.php?id=66211
 +Not only is this not a bug, it isn't even exceptional behavior on the
 +modern web. Users who find this behavior surprising are likely
 +inexperienced with MySQL -- clearly PHP's partner in server-side
 +ubiquity as part of the dominant *AMP stack -- which has the exact
 +same rules for auto-coercion of "numeroalphabetic" strings in a
 +comparison context. 
 +In MySQL (all supported versions):
 +<code sql>
 +SELECT CASE WHEN '-45herearesomeletters' = -45 THEN 'true' ELSE 'false' END
 +prints 'true'
 +There are other popular languages that follow the same
 +casting/coercion rule, though they do not automatically perform the
 +coercion during comparison. For example, JavaScript
 +parseInt('-45herearesomeletters') results in the integer -45. In
 +SQLite, the ubiquitous embedded SQL database, also CAST(
 +'-45herearesomeletters' AS SIGNED ) produces the integer -45.
 +The SQLite documentation explains the logic well: 
 +> When casting a TEXT value to INTEGER, the longest possible prefix of
 +> the value that can be interpreted as an integer number is extracted
 +> from the TEXT value and the remainder ignored. Any leading spaces in
 +> the TEXT value when converting from TEXT to INTEGER are ignored. If
 +> there is no prefix that can be interpreted as an integer number, the
 +> result of the conversion is 0. (http://www.sqlite.org/lang_expr.html#castexpr)
 +And this behavior is not considered particularly "distinctive". (http://sqlite.org/different.html)
 +Since the ubiquity of MySQL has been used to support the expectations
 +users should have of PHP, it's fair to note Oracle, SQL Server, and
 +PostgreSQL will not allow the above comparison to be performed: the
 +statement produces a fatal error. It's a runtime casting error: these
 +languages do not prohibit comparing values of different datatypes, as
 +long as the engine can cast the runtime contents of the value. Yet
 +such implementations, arguably, violate the "least astonishment"
 +concept, since a errant letter modifier like '1A' will cause a fatal
 +error where the expectation might be to either have a '1A' compare
 +equal to 1 (as in MySQL) or fail gracefully (as in SQLite). In this
 +respect, the SQLite behavior is more balanced than that of
 +Oracle/MSSQL/PGSQL, and PHP and MySQL's behavior is graceful,
 +generous, and reasonable.
 +With PHP and MySQL agreeing on this behavior, it is clear that
 +automatically coercing a "numeroalphabetic" string (for want of a
 +better term) to a number via truncation is common practice on the web,
 +even if it is news to the inexperienced user.
 ==== String decrements ==== ==== String decrements ====
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 https://wiki.php.net/rfc/base-convert https://wiki.php.net/rfc/base-convert
 +==== filter_var ====
 +<code php>
 +var_dump(filter_var('01', FILTER_VALIDATE_INT));
 +var_dump(filter_var('01', FILTER_VALIDATE_FLOAT));
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 http://jp2.php.net/min http://jp2.php.net/min
rfc/inconsistent-behaviors.txt · Last modified: 2021/03/27 14:31 by ilutov