In PHP, can someone explain to me why this resolves to true:
'NONE' == 0
+3
A:
Because the string is 0 when evaluated in a number context. Quoting:
If you compare a number with a string or the comparison involves numerical strings, then each string is converted to a number and the comparison performed numerically.
So it depends on what the string contains.
Also, see the chapter on Type Juggling and Type Comparison in the PHP Manual.
Gordon
2010-07-29 15:08:35
As described here: http://www.php.net/manual/en/language.types.string.php#language.types.string.conversion
Mchl
2010-07-29 15:09:51
@Mchl yes, thanks. Added it.
Gordon
2010-07-29 15:12:56
so ... NONE is a keyword? Like 'false'? (I'm asking this while reading the chapter)
Putr
2010-07-29 15:13:45
@Putr no, its a string. nothing more.
Gordon
2010-07-29 15:15:09
@Putr Not really. Any string in a boolean context evaluates to true. So `('false' == false)` is false, `('false' == true)` is true.
NullUserException
2010-07-29 15:17:34
@NullUser it's not a boolean context here though, but a numeric one, so `('10' == 10)` and `('0xFF' == 255)` and `('16 foo' == 16)` is all true.
Gordon
2010-07-29 15:27:21
+12
A:
Because any non-numerical string cast to int will turn into 0.
If you don't want that to happen, use ===, the identical operator.
Read:
http://php.net/manual/en/language.operators.comparison.php
http://php.net/manual/en/types.comparisons.php
NullUserException
2010-07-29 15:10:02
This is just nitpicking, but `is_numeric('16 foo')` is `FALSE`, e.g. a non-numerical string and typecasting it to int will turn it into 16, not 0.
Gordon
2010-07-29 15:33:21
@NullUser not in this case :) it's all described at http://de.php.net/manual/en/language.types.string.php#language.types.string.conversion
Gordon
2010-07-29 15:54:46