Luke schreef:
I wonder if this is a shared trait between C and PHP (since I understand PHP
is written in C) that the break; and the default: are placed for good
practice in all switch statements since they prevent memory leaks?
default is not required, never heard it was good practice to always put it in.
I assume that the fact that php is written in C has no baring on the functionality of
php's switch implementation. *in theory* one should not have to be concerned with mem
leaks when using php, that kind of low level stuff is the exact reason C
isn't generally used to build web apps.
in practice mem leaks can be an issue, but this is generally in long running
cli scripts ... and I don't think breaks left out of switch statements have
ever been shown to be the cause ... that said leaving out a break from
a switch case may completely change the logic of the code, but that's a
seperate issue (see tedd's explaination)
2008/9/10 Jochem Maas <jochem@xxxxxxxxxxxxx>
tedd schreef:
At 6:46 PM -0600 8/31/08, Govinda wrote:
Not that it is an issue, but just to understand the logic-
Why do we have to use 'break' statements in each case?
switch ($i) {
case 0:
echo "i equals 0";
break;
case 1:
echo "i equals 1";
break;
case 2:
echo "i equals 2";
break;
}
all 3 cases fire, even though $i only equals ONE of those case values (if
I said that right).
I mean if $i==1, then in other languages I don't expect the first or last
case to fire! (?)
Is the purpose just so one has the OPTION of letting them all fire, and
turning that off with 'break'?
Or is there a better reason?
-G
The "break" is to separate each case (i.e., condition)
The switch ($i) isn't even needed if you do it like this:
switch (true)
{
case $i==0:
echo "i equals 0";
break;
case $i==1:
echo "i equals 1";
break;
case $i==2:
echo "i equals 2";
break;
}
this is 'true' ;-) and works very well when you want to
check disparate truths but there are caveats:
1. it's less performant IIRC
2. there is no type checking, so auto-casting occurs during the
test of each case's expression
3. it will become even less performant ... someone clever sod has
a patch that heavily optimizes 'simple' switch statements ... see
the internal mailing list archives for details (I can't remember the
details) ... I gather this patch will eventually make it into the core,
if it hasn't already.
If you wanted to combine conditions, you could do this:
switch (1)
{
case $i==-2:
case $i==-1:
case $i==0:
echo "i is less than 0 but greater than -3 and is a counting number
(i.e., no fraction)";
break;
case $i==1:
echo "i equals 1";
break;
case $i==2:
echo "i equals 2";
break;
}
Typed without checking and after my vacation.
Cheers,
tedd
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