CODEWITHSUNDEEP
phpcastingint
Rain
Rain

Reputation: 3936

PHP Type Casting to integer

Can anyone please explain me the logic in this code ?

<?php
 echo ((0.1 + 0.7) * 10) .'<br />';    // 8
 echo (int) ((0.1 + 0.7) * 10) .'<br />'; // 7 why?

 echo ((0.1 + 0.8) * 10) .'<br />'; // 9
 echo (int) ((0.1 + 0.8) * 10) .'<br />'; // 9 why ??
?>

Upvotes: 2

Views: 231

Answers (2)

Ravi Hirani
Ravi Hirani

Reputation: 6539

If we will cast float number to integer then output will be the number before decimal. Means if we will cast 10.9 to integer then output will be 10

You should also refer these functions ceil() , floor() and round().

For more detail, refer below link also,

PHP unexpected result of float to int type cast

Hope it will help you :-)

Upvotes: 1

Matt
Matt

Reputation: 5428

From the manual: http://php.net/manual/en/language.types.float.php

Warning Floating point precision

Floating point numbers have limited precision. Although it depends on the system, PHP typically uses the IEEE 754 double precision format, which will give a maximum relative error due to rounding in the order of 1.11e-16. Non elementary arithmetic operations may give larger errors, and, of course, error propagation must be considered when several operations are compounded. 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.... So never trust floating number results to the last digit, and do not compare floating point numbers directly for equality. If higher precision is necessary, the arbitrary precision math functions and gmp functions are available. For a "simple" explanation, see the » floating point guide that's also titled "Why don’t my numbers add up?"

Upvotes: 1

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