Combinations of If-Else Constructs in PHP

Let the variable $num be able to take values 1, 2, or 3. Let's also assume that for each value we want to output different strings. To solve this problem, you can simply write three if statements without the else construct:

<?php
	$num = 1; // can be 1, 2, or 3
	
	if ($num === 1) {
		echo 'value1'; // will work if $num is 1
	}
	
	if ($num === 2) {
		echo 'value2'; // will work if $num is 2
	}
	
	if ($num === 3) {
		echo 'value3'; // will work if $num is 3
	}
?>

The variable $day contains some number from the interval 1 to 31. Determine which decade of the month this number falls into.