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Possible Duplicate:
PHP unexpected result of float to int type cast
int((0.1+0.7)*10) = 7 in several languages. How to prevent this?

Can someone explain me this???

<?php
echo (int) ((0.1 + 0.7)*10);//displays an output: `7`
?>

I was expecting to see 8 but I got 7 - please explain this behavior.

Is this a special feature from PHP? Or I didn't understand the integer type in PHP?

Thanks.

Community
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Rakesh Sankar
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  • Why down-vote? Do you mind explaining? – Rakesh Sankar Jan 04 '12 at 11:03
  • possible duplicate of [int((0.1+0.7)*10) = 7 in several languages. How to prevent this?](http://stackoverflow.com/questions/6439140/int0-10-710-7-in-several-languages-how-to-prevent-this) and maybe [How computer does floating point arithmetic?](http://stackoverflow.com/questions/6033184/how-computer-does-floating-point-arithmetic) – Felix Kling Jan 04 '12 at 11:04
  • there internal presentation is different. You may interested in reading PHP manual [page](http://php.net/manual/en/language.types.float.php) – Shakti Singh Jan 04 '12 at 11:04
  • http://stackoverflow.com/questions/873747/what-precaution-to-take-when-doing-something-like-price-int-0-10-7-1 – Subhojit Mukherjee Jan 04 '12 at 11:15

1 Answers1

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This question in php manual:

Additionally, rational numbers that are exactly representable as floating point numbers in base 10, like 0.1 or 0.7, do not have an exact representation as floating point numbers in base 2, which is used internally, no matter the size of the mantissa. Hence, they cannot be converted into their internal binary counterparts without a small loss of precision. This can lead to confusing results: for example, floor((0.1+0.7)*10) will usually return 7 instead of the expected 8, since the internal representation will be something like 7.9999999999999991118....

Egor Sazanovich
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