Re: wat is this for a logic

Norbert Pfeiffer writes: > Hallo, > > please my bad excuses English, I assigned babelfish the translation :) > > My question: > see here http://itbw.de/_tests/diverse/check_ext.php3 > > Why is always true (0 == "foo") ? That is not logical for me. > > I wrote this problem 3 time into the German mailing list, > but nobody could explain or wanted it to me. > > Please answers me personally, because I am not entered in the list. > > Thank you for your trouble with the response. > > > With best greetings > > Norbert Pfeiffer > _____________________________________ > www.uris.de pfeiffer@uris.de > 0177-2363368 02292-681769 > ------------------------------------- > e.o.m. Perhaps I should add this to the FAQ. :) The reason is that when you use the == operator, PHP automatically converts the operands (the things you are comparing) to compatible types--in this case, the 0 remains an integer, and is compared against the _integer_ value of "foo". Now, when PHP converts a string to an integer, the result is calculated from the value of any digit characters in the string up to the first non-digit character. For instance, PHP would convert the string "23foo" to the integer 23, and so on. Since the string "foo" has no digits before the first non-digit, the resulting integer is 0. In other words, when you write 0 == "foo", PHP sees 0 == 0. If you did 0 == "23foo", PHP would see 0 == 23. And so on. PHP 4 includes a new operator: ===. This means 'equal and of the same type'. So 0 === "foo" would evaluate as false, since although 0 and "foo" have the same integer values, they are not actually both of the same type. For more information on these conversions, read: http://www.php.net/manual/de/language.types.type-juggling.php http://www.php.net/manual/de/language.types.string.php#language.types.string.conversion Hope this helps explain it, Torben -- +----------------------------------------------------------------+ |Torben Wilson <torben@php.net> Netmill iTech| |http://www.coastnet.com/~torben http://www.netmill.fi| |Ph: 1 250 383-9735 torben@netmill.fi| +----------------------------------------------------------------+