Using PHP fmod() Function to Compute Floating‑Point Remainder

In PHP, the fmod() function is used to calculate the remainder of two floating‑point numbers. Its syntax is: float fmod ( float $x , float $y ) The parameter $x is the dividend and $y is the divisor; the function returns the remainder of $x divided by $y as a floating‑point value.

The return type of fmod() is a float.

Note that fmod() works only with floating‑point numbers. For integer remainders, use the % operator.

Example 1:

$x = 10.5;
$y = 3.2;
$result = fmod($x, $y);
echo $result; // outputs 1.7

This example shows that dividing 10.5 by 3.2 yields a remainder of 1.7.

Example 2:

$x = 7.2;
$y = 1.5;
$result = fmod($x, $y);
echo $result; // outputs 0.9

Here, the remainder of 7.2 divided by 1.5 is 0.9.

When the divisor is zero, fmod() returns NAN (Not a Number).

Example 3 (divisor zero):

$x = 5.5;
$y = 0;
$result = fmod($x, $y);
echo $result; // outputs NAN

This demonstrates the special handling of a zero divisor.

The function also has specific rules for negative numbers.

Example 4 (negative dividend):

$x = -5.5;
$y = 2.2;
$result = fmod($x, $y);
echo $result; // outputs -1.1

In this case, the remainder of -5.5 divided by 2.2 is -1.1.

In summary, fmod() computes the floating‑point remainder of two numbers, returns a float, cannot be used for integer remainders, returns NAN when the divisor is zero, and follows particular rules for negative values.