How to gain consistency with floats in PHP between servers?

I was working with floats in PHP when I noticed that one server I am on treats them differently. How do I gain consistency between the two servers?

EXAMPLE CODE

$var = "6.15";

var_dump(round($var, 2));
var_dump(floatval($var));

ini_set('serialize_precision', 3); //I don't understand this and would rather not use it

var_dump(round($var, 2));
var_dump(floatval($var));

SERVER 1 RESULTS - Linux - PHP Version 8.1.12

float(6.1500000000000004)
float(6.1500000000000004)
float(6.15)
float(6.15)

SERVER 2 RESULTS - Linux - PHP Version 7.3.25

float(6.15)
float(6.15)
float(6.15)
float(6.15)

source https://stackoverflow.com/questions/76113903/how-to-gain-consistency-with-floats-in-php-between-servers