Re: [PHP] Re: Weird comparison error.
Lars Torben Wilson [EMAIL PROTECTED] wrote in message news:[EMAIL PROTECTED] On Sat, 2003-06-28 at 11:28, Bobby Patel wrote: In PHP there are two operators for comparisons, the double and triple equivalance. Double equivalance just check's the boolean type so if (0 == 'n') is translated to if (False == False), where as triple equivalance checks the data types as well so if (0==='n') becomes if (Int(False)==String(False)) but since the data types don't match that would be False. to get a better reference check PHP.net for 'Bolean Types' , because I think I dodn't explain the double equivalance right, and also it will clarify situations of the Null type. Bobby You got pretty close, but not quite. :) In the case of the equality operator '==', there is nothing specific to do with boolean evaluation going on. It just converts the string to its integer value implicitly before checking for equality, and according to the string-integer conversion rules, the string ends up being (int) 0 so the whole thing matches. Also, it might be easier to think about the identical operator '===' as just testing whether two values are identical, meaning that they are both of the same type, and that they both have the same value. Yeah, I understand the difference between the double and triple '='. I was just surprised to find that when comparing what was two string values, because one of the strings was '0', it decided to convert both strings to an integer. I'll just have to use the '===' or strcmp from now on. More information: http://www.php.net/manual/en/language.types.type-juggling.php http://www.php.net/manual/en/language.types.string.php#language.types.string.conversion ...in fact, the whole 'Language' section of the manual has a bunch of stuff on this. Hope this helps, Thanks. Torben -- Rob -- PHP General Mailing List (http://www.php.net/) To unsubscribe, visit: http://www.php.net/unsub.php
[PHP] Re: Weird comparison error.
In PHP there are two operators for comparisons, the double and triple equivalance. Double equivalance just check's the boolean type so if (0 == 'n') is translated to if (False == False), where as triple equivalance checks the data types as well so if (0==='n') becomes if (Int(False)==String(False)) but since the data types don't match that would be False. to get a better reference check PHP.net for 'Bolean Types' , because I think I dodn't explain the double equivalance right, and also it will clarify situations of the Null type. Bobby Rob Adams [EMAIL PROTECTED] wrote in message news:[EMAIL PROTECTED] I don't need anything fixed, I'm just curious about something I noticed. I'm doing a comparison between a variable and a hard coded char. Like this: if ($k1 == n) The variable is usually the first key in an array (0) so it should usually evaluate false, but it was true every time until I changed it to: if ($k1 === n) So I'm assuming that it decided that since $k1 was an int to convert n to an int (which would be 0) and conclude that 0 does indeed equal n. So I decided for fun to try: if (n == $k1) And it still was true everytime. So why does it always try convert my literal to an int instead of use the variable as a string? Just curious. Thanks. -- Rob -- PHP General Mailing List (http://www.php.net/) To unsubscribe, visit: http://www.php.net/unsub.php
Re: [PHP] Re: Weird comparison error.
On Sat, 2003-06-28 at 11:28, Bobby Patel wrote: In PHP there are two operators for comparisons, the double and triple equivalance. Double equivalance just check's the boolean type so if (0 == 'n') is translated to if (False == False), where as triple equivalance checks the data types as well so if (0==='n') becomes if (Int(False)==String(False)) but since the data types don't match that would be False. to get a better reference check PHP.net for 'Bolean Types' , because I think I dodn't explain the double equivalance right, and also it will clarify situations of the Null type. Bobby You got pretty close, but not quite. :) In the case of the equality operator '==', there is nothing specific to do with boolean evaluation going on. It just converts the string to its integer value implicitly before checking for equality, and according to the string-integer conversion rules, the string ends up being (int) 0 so the whole thing matches. Also, it might be easier to think about the identical operator '===' as just testing whether two values are identical, meaning that they are both of the same type, and that they both have the same value. More information: http://www.php.net/manual/en/language.types.type-juggling.php http://www.php.net/manual/en/language.types.string.php#language.types.string.conversion ...in fact, the whole 'Language' section of the manual has a bunch of stuff on this. Hope this helps, Torben -- Torben Wilson [EMAIL PROTECTED]+1.604.709.0506 http://www.thebuttlesschaps.com http://www.inflatableeye.com http://www.hybrid17.com http://www.themainonmain.com - Boycott Starbucks! http://www.haidabuckscafe.com - -- PHP General Mailing List (http://www.php.net/) To unsubscribe, visit: http://www.php.net/unsub.php
