Description:
------------
---
From manual page: https://php.net/function.fmod
---
PHP 5.2.x through PHP 7.3.2 still the same problem.

Code:
<?php
echo fmod(-25, 0.2); // -0.2, should be 0
echo -25 - floor(-25/0.2) * 0.2; // 0, as it should be
?>

Default installation of OSPanel (OpenServer 5.2.2) with default configuration of php.ini and etc in it.

Documentation says:

"Returns the floating point remainder of dividing the dividend (x) by the divisor (y). The remainder (r) is defined as: x = i * y + r, for some integer i. If y is non-zero, r has the same sign as x and a magnitude LESS than the magnitude of y."

But r magnitude EQUAL to y.

Solution:
function fmod($x, $y){return echo $x - floor($x/$y) * $y;} 

Test script:
---------------
<?php 
echo var_dump(fmod(21, 0.2) == 0); // bool(false)
echo var_dump(fmod(1, 0.1) == 0); // bool(false)
echo fmod(1, 0.1); // 0.1
echo fmod(1, 0.2); // 0.2

Expected result:
----------------
<?php 
echo var_dump(fmod(21, 0.2) == 0); // bool(true)
echo var_dump(fmod(1, 0.1) == 0); // bool(true)
echo fmod(1, 0.1); // 0
echo fmod(1, 0.2); // 0

Actual result:
--------------
bool(false)
bool(false)
0.1
0.2