Why i not get same value with $x and $y PHP var?

Question

When i tested this code , i get $x = 29 and $y = 30 .

.

<?PHP
$x = "0.0003";
$x = $x*100000;
$x = floor($x);
echo $x;
?>

<br>

<?PHP 
$y = "30";
$y = floor($y);
echo $y;
?>

Why $x not 30 ? what's happen ?

How can i do for get $x = 30