PHP switch case - flawed or valid? [duplicate] - php

Question

This question already has answers here:
Why was the switch statement designed to need a break?
(9 answers)
Closed 8 years ago.
I don't understand why a switch-case statement requires you to explicitly insert a break after each case. Isn't the whole point of it to stop once a case is made?
Can someone give me a circumstance where a case is found true but for some reason [you insert reason here] you still need the code block to execute through.
This is a vaild PHP switch-case statement
switch ($error) {
case 'empty':
$msg = 'Field cannot be empty.';
break;
case 'invalid':
$msg = "Field may only contain number.";
break;
}
This is a invaild PHP switch-case statement
switch ($error) {
case 'empty':
$msg = 'Field cannot be empty.';
case 'invalid':
$msg = "Field may only contain number.";
}
So is this break useless or does it serve a purpose in some situations?

Answer 1

Because that's just how it works - it's how the language was designed. Probably because that's how C did it.
The most common use is for two cases to be treated the same.
switch ($error) {
// Treat warnings and errors the same
case 'warning':
case 'error':
echo "Something went wrong.";
break;
}

Answer 2

I believe this question is a duplicate to this one, answered robustly by #Micahel Burr :
Many answers seem to focus on the ability to fall through as the reason for requiring the break statement.
I believe it was simply a mistake, due largely because when C was
designed there was not nearly as much experience with how these
constructs would be used.
Peter Van der Linden makes the case in his book "Expert C
Programming":
We analyzed the Sun C compiler sources to see how often the default
fall through was used. The Sun ANSI C compiler front end has 244
switch statements, each of which has an average of seven cases. Fall
through occurs in just 3% of all these cases.
In other words, the normal switch behavior is wrong 97% of the time.
It's not just in a compiler - on the contrary, where fall through was
used in this analysis it was often for situations that occur more
frequently in a compiler than in other software, for instance, when
compiling operators that can have either one or two operands:
switch (operator->num_of_operands) {
case 2: process_operand( operator->operand_2);
/* FALLTHRU */
case 1: process_operand( operator->operand_1);
break; }
Case fall through is so widely recognized as a defect that there's
even a special comment convention, shown above, that
tells lint "this is really one of those 3% of cases where fall through
was desired."
I think it was a good idea for C# to require an explicit jump
statement at the end of each case block (while still allowing multiple
case labels to be stacked - as long as there's only a single block of
statements). In C# you can still have one case fall through to another
- you just have to make the fall thru explicit by jumping to the next case using a goto.
It's too bad Java didn't take the opportunity to break from the C
semantics.

Answer 3

It's also used for combinatory conditions.
To give a somewhat useless example:
// manually total up a number by 1
$sum = 0;
switch ($number) {
case 4:
$sum += 1;
case 3:
$sum += 1;
case 2:
$sum += 1;
case 1:
$sum += 1;
}
This sets switch apart from exclusive if trees in that one case can be a superset of another, and reduces code duplication. If all your cases contain a break, then you can certainly transpose it into an if list. (switch is often just utilized for stylistic reasons).

Answer 4

A single statement can carry multiple case labels, as the following example shows where we are not using break:
switch($constant)
{
case 'a' :
case 'b' :
case 'c' :
case 'd' :
case 'e' :
case 'f' : hexcvt(c);
}
In this example, if constant-expression equals any letter between 'a' and 'f', the hexcvt function is called.