Originally Posted by

**php.net/float**
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....

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