'210010106140040100' == '210010106140040101'
Posted on
16th Feb 2014 07:03 pm by
admin
Debugging this simple line of a PHP script
Code: if($a == $b){ }
I've found that with value of
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$a = '210010106140040100' (type = string)
$b = '210010106140040101' (type = string)
the result of the comparison is TRUE
the same if i compare 2 integer
$a = 210010106140040100 (type = int)
$b = 210010106140040101 (type = int)
$a == $b ( true )
If I use the === operator
'210010106140040100' === '210010106140040101' (comparison of strings: result is FALSE)
210010106140040100 === 210010106140040101 (comparison of numbers: result is TRUE)
I think it could be caused by the fact that the string is 'like' integer, but exceed the standard size of integer number.
But the final result remain a mistery for me: I've tested some others 'big' numbers and I've found for example:
18014398509481980==18014398509481981 (true) !!!!
18014398509481982==18014398509481981 (false) !!!!
In my specific script i can handle this specific comparison using the === operator, because i can assume that the variable are string.
But i'd like to know why this happen, and i'd appreciate suggestions about how to efficiently compare 'big' integers.
Thanks!
I use PHP 5.2 with IIS
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