Am 19.08.2014 16:46, schrieb Toby Hart Dyke: > > But what does "\0" mean, and where is it documented? In this context, it > clearly means zero, but not false, so the intention is to check for the > presence of the tested string. > > It seems that the backslash means to treat as a literal zero character, > which then gets treated as a "true" zero value, rather than a false. I > get PHP's dynamic typing, but this seems a bit tortuous, and I would > always use your idiom ( !== false) whic is much more the PHP way. "\0" is a string consisting of a single NUL-Byte (ASCII code 0). The notation is an escape sequence, which are documented in the manual section about strings[1]. What actually happens in the expression is caused by PHP's type juggling[2]. strpos() returns either a number or false. When a number and a string are loosely compared, the string is converted to a number first, and then a numeric comparison is done. When a boolean value is loosely compared with a string, the string is converted to a boolean before doing the comparison (where false < true).[3] When being converted to boolean, the string "0" is converted to false, and the string "\0" is converted to true. When being converted to a number, however, both strings are converted to 0. Anyway, I would not rely on this particular behavior of casting "\0" to 0 resp. true. IMHO that is somewhat counter-intuitive. Comparison with !== false or maybe > -1 seems to be more sensible here, even though the latter relies on the fact, that -1 is converted to true, which might be surprising. Please do not top post[4]. [1] <http://php.net/manual/en/language.types.string.php#language.types.string.syntax.double> [2] <http://php.net/manual/en/language.types.type-juggling.php> [3] <http://php.net/manual/en/language.operators.comparison.php> [4] <http://git.php.net/?p=php-src.git;a=blob_plain;f=README.MAILINGLIST_RULES;hb=HEAD> -- Christoph M. Becker -- PHP Windows Mailing List (http://www.php.net/) To unsubscribe, visit: http://www.php.net/unsub.php
