PHP If statement that on has variables

i need help with this, currently my idea here is to only use variables to perform an IF statement, these variables are supposed to be taken from a database (ive got that down) but i dont know how to create an if statement that can use all 3

<?php
$Anum="10";
$Bnum="30";
$MOD="<=";

if ($Anum $MOD $Bnum)
{
echo $Anum, " is smaller than ", $Bnum;
}
else
{
echo "$Anum, " is not smaller than ", $Bnum;
}
?>