Optionality of Break in PHP

The break command is optional. However, without it, the behavior of the case blocks will be unexpected. Let's look at an example. Suppose we have the following code:

<?php
	$num = 1;
	
	switch ($num) {
		case 1:
			echo 1;
		break;
		case 2:
			echo 2;
		break;
		case 3:
			echo 3;
		break;
	}
?>

Let's remove all break from it, and to start, let's assign the number 3 to the variable $num.

For now, everything will work as it did:

<?php
	$num = 3; // let the number be 3 here
	
	switch ($num) {
		case 1:
			echo 1;
		case 2:
			echo 2;
		case 3:
			echo 3;
	}
	
	// After running, the code will output 3 - all good
?>

Now let's assign the number 2 to the variable $num. In this case, case 2 will execute as expected, and then, unexpectedly, case 3 will also execute:

<?php
	$num = 2;
	
	switch ($num) {
		case 1:
			echo 1;
		case 2:
			echo 2;
		case 3:
			echo 3;
	}
	
	// After running, the code will output 2, and then 3
?>

If we assign the number 1 to the variable $num, then all case constructs will execute:

<?php
	$num = 1;
	
	switch ($num) {
		case 1:
			echo 1;
		case 2:
			echo 2;
		case 3:
			echo 3;
	}
	
	// After running, the code will output 1, then 2, and then 3
?>

So it turns out that in the absence of break, after the intended case is executed, all case blocks below it will also execute. Sometimes this feature is used when solving problems.

In the next example, if the variable $num has the value 1 or 2, then the value 'a' will be assigned to the variable $res. If the variable $num has the value 3, then the value 'b' will be assigned to the variable $res:

<?php
	$num = 1;
	
	switch ($num) {
		case 1:
		case 2:
			$res = 'a';
		break;
		case 3:
			$res = 'b';
		break;
	}
	
	echo $res;
?>

Above I wrote that sometimes this feature is used, but I, generally speaking, do not recommend using it, as the code becomes not very obvious.

It is more obvious to solve such a problem with ifs:

<?php
	$num = 1;
	
	if ($num == 1 or $num == 2) {
		$res = 'a';
	}
	
	if ($num == 3) {
		$res = 'b';
	}
	
	echo $res;
?>