Apr 282010
Floating point precision in PHP
Answer:
It is typical that simple decimal fractions like 0.1 or 0.7 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 7.9.
E.g.
$a = 0.1;
$b = 0.7;
print $a + $b;
print (( $a + $b ) * 10);
Reference: http://www.php.net/manual/en/language.types.float.php
So, never compare two floating numbers in your program.
