math - PHP float calculation error when subtracting

Tuesday, 18 December 2018

I have a very strange issue. If I subtract 2 float vars where one is the result of a mathematical operation I get a wrong value.

Example:

var_dump($remaining);
var_dump($this->hours_sub['personal']);
echo $remaining-$this->hours_sub['personal'];

This it the output:

float 5.4
float 1.4
5.3290705182008E-15

5.4-1.4 should be 4
If I add the two values the result is correct.

Where is my mistake?
It can not be a rounding issue.

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