This is how to format a number to x amount of decimal places, this is a particularly good example

<?php
$pi=3.1415926535897932384626433832795;
//6 decimal places
echo number_format($pi,6);
echo "<br>";
//3 decimal places
echo number_format($pi,3);
?>

Example

"; //3 decimal places echo number_format($pi,3); ?>