Floating Point Numbers
Floating point numbers, also known as floats, doubles, or real numbers, can be specified using a decimal dot and a mantis.
They may also use a number separator _: it may be placed anywhere between two digits, to help make the number more readable.
Floats used to be called real, though this was abandoned progressively, since PHP 7.0.
<?php
$a = 1.234;
$b = 1.2e3;
$c = 7E-10;
$d = 1_234.567; // as of PHP 7.4.0
?>