switch

The switch statement is similar to a series of IF statements on the same expression. In many occasions, you may want to compare the same variable (or expression) with many different values, and execute a different piece of code depending on which value it equals to. This is exactly what the switch statement is for.

Замечание: Note that unlike some other languages, the continue statement applies to switch and acts similar to break. If you have a switch inside a loop and wish to continue to the next iteration of the outer loop, use continue 2.

The following two examples are two different ways to write the same thing, one using a series of if and elseif statements, and the other using the switch statement:

Пример 16-1. switch structure

<?php
if ($i == 0) {
   echo "i equals 0";
} elseif ($i == 1) {
   echo "i equals 1";
} elseif ($i == 2) {
   echo "i equals 2";
}

switch ($i) {
case 0:
   echo "i equals 0";
   break;
case 1:
   echo "i equals 1";
   break;
case 2:
   echo "i equals 2";
   break;
}
?>

Пример 16-2. switch structure allows usage of strings

<?php
switch ($i) {
case "apple":
   echo "i is apple";
   break;
case "bar":
   echo "i is bar";
   break;
case "cake":
   echo "i is cake";
   break;
}
?>

It is important to understand how the switch statement is executed in order to avoid mistakes. The switch statement executes line by line (actually, statement by statement). In the beginning, no code is executed. Only when a case statement is found with a value that matches the value of the switch expression does PHP begin to execute the statements. PHP continues to execute the statements until the end of the switch block, or the first time it sees a break statement. If you don't write a break statement at the end of a case's statement list, PHP will go on executing the statements of the following case. For example:

<?php
switch ($i) {
case 0:
   echo "i equals 0";
case 1:
   echo "i equals 1";
case 2:
   echo "i equals 2";
}
?>

Here, if $i is equal to 0, PHP would execute all of the echo statements! If $i is equal to 1, PHP would execute the last two echo statements. You would get the expected behavior ('i equals 2' would be displayed) only if $i is equal to 2. Thus, it is important not to forget break statements (even though you may want to avoid supplying them on purpose under certain circumstances).

In a switch statement, the condition is evaluated only once and the result is compared to each case statement. In an elseif statement, the condition is evaluated again. If your condition is more complicated than a simple compare and/or is in a tight loop, a switch may be faster.

The statement list for a case can also be empty, which simply passes control into the statement list for the next case.

<?php
switch ($i) {
case 0:
case 1:
case 2:
   echo "i is less than 3 but not negative";
   break;
case 3:
   echo "i is 3";
}
?>

A special case is the default case. This case matches anything that wasn't matched by the other cases, and should be the last case statement. For example:

<?php
switch ($i) {
case 0:
   echo "i equals 0";
   break;
case 1:
   echo "i equals 1";
   break;
case 2:
   echo "i equals 2";
   break;
default:
   echo "i is not equal to 0, 1 or 2";
}
?>

The case expression may be any expression that evaluates to a simple type, that is, integer or floating-point numbers and strings. Arrays or objects cannot be used here unless they are dereferenced to a simple type.

The alternative syntax for control structures is supported with switches. For more information, see Alternative syntax for control structures .

<?php
switch ($i):
case 0:
   echo "i equals 0";
   break;
case 1:
   echo "i equals 1";
   break;
case 2:
   echo "i equals 2";
   break;
default:
   echo "i is not equal to 0, 1 or 2";
endswitch;
?>



switch
scott at firefallpro dot com
22-Dec-2005 12:01
It's has already been mentioned indirectly in a few posts, but it is important to realize that switch statements evaluate each case with the "==" operator by default. This can lead to unexpected results when comparing strings to integers, because PHP will convert the string to an integer. In many cases this means a string can be equivalent to the integer 0.

Example:
<?php
$x = 0;

switch($x) {
case "a":
   echo "a";
   break;
case "b":
   echo "b";
   break;
default
   echo "default";
}
?>

The result will be an "a" echoed out. What PHP does in this instance, is once it realizes that it's attempting to compare string ("a") to an integer (0), it converts "a" into an integer which ends up satisfying the first case.

The rules for string conversion into integers is available at:
http://us3.php.net/manual/en/language.types.string.php

The easiest way to combat this issue is to force type comparison by using the "===" operator. This makes PHP forego the string to integer conversion.

Example:
<?php
switch(true) {
case $x === "a":
   echo "a";
   break;
case $x === "b":
   echo "b";
   break;
default
   echo "default";
}
?>

Or the switch input can be type-casted to always be a string, etc.

Also note that even though a conditional statement needs to be explicitly set in each case to gain expected behavior, the switch can still execute faster then an "ifelse" block because PHP will not continue to evaluate conditions once a case has been satisfied.
jonybd at yahoo dot com
28-Jun-2005 05:25
/*
   Have one value need to deal with currency
   - follow as example
*/
while ($row = mysql_fetch_array($v_Result,MYSQL_NUM)) {
   $v_BAL = $row[1]/10000;
  
   switch (TRUE){

       case ($v_BAL <= 0):            //less then 0 , -0
           echo $v_BAL;
       break;
                  
       case ($v_BAL <= 10 AND $v_BAL >= 1):    //less then 10 and greater then 1
           echo $v_BAL;
       break;
                                      
       default:                //default
           echo $v_BAL;
       break;
   }
}
dohpaz at kennethpaul dot com
04-Jun-2005 03:24
[Editor's note: Changed the second switch to make it work as intended.]

I haven't seen anything specifically pointing this out, but you can get a small performance increase in your code by re-structuring your complex switch statements.

For example, I was using the following switch to convert textual month names into their numerical counterparts from the Date header of email on my pop server:

switch ($month_name) {
  case "Jan":
  case "January":
   $month = "1";
   break;
  ...
}

Even just looping through 15 emails on the server, it would take upwards of around 9-10 seconds! So, I decided to shorten my switch statement to something like this:

switch (TRUE) {
  case ($month_name == "Jan" || $month_name == "January"): $month = "1"; break;
  ...
}

Doing this I actually shaved 3 seconds from my script's execution time!!! I thuoght this was well worth noting for other coders out there who are looking to optimize their PHP code.
ant at loadtrax dot com
24-Mar-2005 09:01
This caught me out. The number '6' when compared with the string '6b' returns true. The solution is to either typecast the compare  -  ie, " switch ((string)$type): "  or to make sure $type is a string (eg $type="6")

<?
$type=6;
switch ($type):
   case "6b":
       print "6b: ";
       print $type;
   break;
   case "6":
       print "6: ";
       print $type;
   break;
endswitch;
?>
Bruno Feu
22-Mar-2005 01:22
You can solve the problem by just writing the following piece of code:

<?php
$x = 18;
$y = 6;

switch ($x) {
   case ($y * 4):
   case (9 * 3):
       echo "Member";
       break;
   default:
       echo "Not a member";
}
?>
ach aat bitfabrik doot de
14-Mar-2005 03:21
So instead of writing the code shown below it would have to be like this:

<?php
$x = 18;
$y = 6;

switch ($x) {
   case ((($y * 4) || (9 * 3))?$x:false):
       echo "Member";
       break;
   default:
       echo "Not a member";
}
?>

So now the case expression contains an if statement in simplified notation which either returns the value of $x if the expression is true (so the case matches) or false, if the expression was false (so the case does not match).
Be aware that it only works if $x never actually is "false" because then it would match in either case. So the "false" in the above code should always be any random value which is not a possible value for $x.
gregory dot mccoy at pleasedontspam dot cafeoui dot net
13-Mar-2005 09:07
In the post:
----------------------------------------------------
design at hyperoptix dot com
18-Feb-2004 12:46
Boolean logic does not work inside case statements:

<?php
$x = 18;
$y = 6;

switch ($x) {
   case (($y * 4) || (9 * 3)):
       echo "Member";
       break;
   default:
       echo "Not a member";
}
?>

echoes "Member".
----------------------------------------------------
there were many responses but all seem to miss the point.  You cannot mix apples and oranges.  The "switch($x)" establishes that this "switch" statement will be a Relational syntax while the "case" qualifier uses a Logical syntax.  There must be a match.  Either change "switch($x)" to "switch(true)" or change "case(($y * 4) || (9 * 3)):" to resolve to a value.

The syntax of the original post is like a cop that says, "I want all of your answers to reflect truth.  So, are you eighteen?"  The respondent says, " 4 x 4 or 11 + 5".  Need I say more?
rdoggett at oz dot net
19-Jan-2005 05:01
Here's an often overlooked way of doing (nearly) the same thing:
<?php
echo ($i == 0) ?  "i is zero" :
     (($i == 1) ?  "i equals 1" :
     (($i == 2) ?  "i equals 2" : ""));
?>
This may be an idiomatic surprise at first.  But the clean and concise code speaks for itself.

Beware; PHP seems to parse the ternary operator with a different precedence than other languages such as C or perl or javascript.  This means PHP requires nested parenthesis around each nested group to avoid unexpected results.  Even so, this construct is still very understandable and maintainable, compared to the equivalent switch or if statements.
Derek Ethier
22-Dec-2004 11:43
A word of caution around the order used for the case/default controls.  I notice that a lot of people do not break; the default section and the following could lead to incorrect results when run.

$a = "lowercase";

switch ( $a ) {
  default:
   $a = strtoupper( $a );
   print $a . "<br />";

  case ( 'LOWERCASE' ):
   print $a . "<br />";
   break;
}

Result:
LOWERCASE
LOWERCASE

Placing a break; in the default control will result in:
LOWERCASE

.. as expected.  Also, placing the default section at the bottom (as in an else control) will also display the correct result.
Bachsau
20-Dec-2004 04:52
Be carefull: If you want to test the return of a function, you have to use switch, because if you use 'if' and 'ifelse', your function will be executed every time again.

For example if use use the following construct:

if(file_get_contents('file.htm', 0) == 'typ1') {
     // Do one thing
}
ifelse(file_get_contents('file.htm', 0) == 'typ2') {
     // Do the second thing
}
ifelse(file_get_contents('file.htm', 0) == 'typ3') {
     // Do the third thing
}

The file will be requested 3 times!!!

If you use the following:

switch (file_get_contents('file.htm', 0)) {
     case 'typ1': // Do one thing
     break;
     case 'typ2': // Do the second thing
     break;
     case 'typ3': // Do the third thing
}

The file will be requested only once!!!
pentek_imre at mailbox dot hu
23-Oct-2004 04:25
Using select is like using == (instead of ===) in an if statement. Let's see an example:
<?php
function Describe($Q)
{
  var_dump($Q);
  echo ": ";
  switch ($Q)
   {
   case "0":
     echo "String zero";
     break;
   case 0:
     echo "Integer zero";
     break;
   case NULL:
     echo "NULL NULL";
     break;
   case FALSE:
     echo "Boolean FALSE";
     break;
   case "":
     echo "Empty string";
     break;
   default:
     echo "Any other value";
     break;
   }
  echo "<BR>\n";
}
Describe("0");
Describe(0);
Describe(NULL);
Describe(FALSE);
Describe("");
Describe(1);
?>
Output (PHP 5.0.1) is:
string(1) "0" : String zero
int(0) : String zero
NULL : Integer zero
bool(false) : String zero
string(0) "" : Integer zero
int(1) : Any other value
tom AT csbanana DOT com
11-Oct-2004 10:18
If you're using switch() inside a function and you're returning a $var inside each case, you won't need to include break() as return() will end the execution of the switch and function.
manicdepressive at mindless dot com
21-Apr-2004 04:43
Be careful if distinguishing between NULL and (int)0.  As implied in the above documentation, the case statements are equivalent to the '==' operator, not the '===' operator, so the following code did not work as i expected:

<?php
$mixed = 0;
switch($mixed){
   case NULL: echo "NULL";  break;
   case 0: echo "zero";  break;
   default: echo "other"; break;
}
?>

Instead, I may use a chain of else-ifs.  (On this page, kriek at jonkreik dot com states that "in most cases [a switch statement] is 15% faster [than an else-if chain]" but jemore at m6net dotdot fr claims that when using ===, if/elseif/elseif can be 2 times faster than a switch().)

Alternatively, if i prefer the appearance of the switch() statement I may use a trick like the one nospam at please dot com presents:

<?php
$mixed = 0;
switch(TRUE){
   case (NULL===$mixed): //blah break;
   case (0  ===$mixed): //etc. break;
}
?>

code till dawn! mark meves!
ezekiel at superquenelles dot com
25-Mar-2004 05:40
In reply to Alex Fung :
The following code doesn't work :

<?php
$x = 18;
$y = 6;

switch ($x) {
   case (($y * 4) || (9 * 3)):
       echo "Member";
       break;
   default:
       echo "Not a member";
}
?>

Why :
<design at hyperoptix dot com> want to test if $x == $y*4 or $x == 9*3 ($x == (($y*4)||(9*3))
However the case statement evaluate the value of (($y*4)||(9*3)) that is always true because 9*3=27 (!=0)
That's why this code always return true when $x != 0.
The correct code would be :

<?php
$x = 18;
$y = 6;

switch ($x) {
   case (($y * 4)):
   case ((9*3)):
       echo "Member";
       break;
   default:
       echo "Not a member";
}
?>

Boolean logic work inside case statement, you just need to know that the expression in the case statement is first evaluated then compared with the evaluated value in the switch statement.
php dot net dot 1 at yogelements dot com
19-Jan-2004 10:39
Declaring a variable (actually an array) as static w/in a switch{} spun my wool for a while:
don't:
<?
function ss() {
   switch ("bug") {
       case "bug" :
           static $test = "xyz";
           break;
       default :
           static $test = "abc";
   }
 echo $test;
}
ss(); //abc
?>
do:
<?
function tt() {
   static $test;
   switch ("fix") {
       case "fix" :
           $test = "xyz";
           break;
       default :
           $test = "abc";
   }
 echo $test;
}
tt(); // xyz
?>
gmgiles at pacbell dot net
19-Jan-2004 01:07
Did you know that switch() and case() can also accomodate things like basic math calculations and counter incrementing? They do. In this example, I use a switch statement (which is inside of a while loop) to alternate the background color of a table row. It gives me a cool spool-printer-paper effect.

<?php
$rows_per_color = 5;  // change bgcolor every 5 rows
switch($ctr++) {
   case 0:
       $bgcolor = "#ffffff";
       break;
   case ($rows_per_color):
       $bgcolor = "#ff0000";
       break;               
   case ($rows_per_color * 2):
       $bgcolor = "#ffffff";
       $ctr = 1;
       break;       
}
?>

As you can see, I increment $ctr by 1 in the switch() itself, and the final case() does a simple calculation. Simple, but powerful. [Remember, the above example is inside of a while() loop... each time it iterates, switch increments $ctr.]
phpmanual at nos-pam dot sadlittleboy dot com
10-Jan-2004 05:32
Regarding bishop's comment below, although using:
   switch($bug === 0 ? '' : $bug) {
may work, ( and although I do like the ternary operator, :) it might be more intuitive/readable to use this instead:
   switch( (string)$bug ) {
which typecasts the variable to a string to ensure that "0" will be handled correctly.
jon
08-Dec-2003 12:48
In response to the entry by "kriek at jonkriek dot com", I think you would probably be better of doing this:
<?php
   // ensure $_GET['go'] is set, an integer, and not 0
   // then, set nav number; default to 1
   $nav = ( isset($_GET['go']) && (intval($_GET['go']) == $_GET['go']) && $_GET['go'] ) ?
       intval($_GET['go']) : 1;

   // format navigation string and include
   include(sprintf("Page%02d.php",$nav));   
?>

... as oppposed to the switch setup you recommended, which is limited to the number of cases you specify...
havar at henriksen dot nu
14-Sep-2003 01:54
Remember, that you also could use functions in a switch.
For example, if you need to use regular expressions in a switch:

<?php
$browserName = 'mozilla';
switch ($browserName) {
  case 'opera':
   echo 'opera';
  break;
  case (preg_match("/Mozilla( Firebird)?|phoenix/i", $browserName)?$browserName:!$browserName):
   echo "Mozilla or Mozilla Firebird";
  break;
  case 'konqueror':
   echo 'Konqueror';
  break;
  default:
   echo 'Default';
  break;
}
?>

or you could just use a regular expression for everything:

<?php
$uri = 'http://www.example.com';
switch (true) {
  case preg_match("/$http(s)?/i", $uri, $matches):
   echo $uri . ' is an http/https uri...';
  break;
  case preg_match("/$ftp(s)?/i", $uri, $matches):
   echo $uri . ' is an ftp/ftps uri...';
  break;
  default:
   echo 'default';
  break;
}
?>
(cgibbard) student math uwaterloo ca
10-Aug-2003 02:30
Just in reply to the comment about 2 digit numbers: something octal certainly is going on. Integer literals prefixed with a "0", like in C and several other languages, are treated as octal. Similarly, integer literals prefixed with "0x" are treated as hexadecimal. Seeing as this is the case, 08 and 09 are not valid integer literals. It turns out that php treats them as 0 (it would probably be better to fail with an error message, but it doesn't). Bottom line? Don't prefix numbers with 0 in code unless you mean octal. Format them as you print them with printf, like so: printf("%02u", $my_unsigned_int); or if you will, use sprintf to get a string representation rather than printing on stdout.
bishop
14-Jul-2003 12:26
As jason at devnetwork dot net and others have pointed out, using switch() when you wish to compare against strings can be dangerous:

<?php
$bug = 0;
switch ($bug) {
   case 'fly':
       echo 'flies buzz';
       break;

   case 'mantis':
       echo 'mantes pray';
       break;

   default:
       echo 'swat, splat, you are dead';
       break;
}
?>

Will print "flies buzz", NOT "swat, splat, you are dead".
Remember PHP says that 'fly' == 0, or in general string == 0 is true.

Anyway, avoid that with:

<?php
$bug = 0;
switch ($bug === 0 ? '' : $bug) {
   case 'fly':
       echo 'flies buzz';
       break;

   case 'mantis':
       echo 'mantes pray';
       break;

   default:
       echo 'swat, splat, you are dead';
       break;
}
?>

Prints out what you expect:

Swat
Splat
You are dead

P.S.: that's an empty string (single quote single quote), not a spurious double quote.
shawn at evilest dot net
04-May-2003 02:50
You can also nest switch statements inside case statements:

<?php
   // Set argument handlers
   $argv = explode(",", urldecode(getenv('QUERY_STRING')));
   $argc = array_shift($argv);
   $argd = array_shift($argv);
   $arge = array_shift($argv);
?>

   // Begin switching

<?php
   switch ($argc) {
       case 'home': {
             print('This is $argc, home case.');
           break;
       }
       case 'subsection': {
               switch ($argd) {
                     case 'links': {
                           switch($arge) {
                               case 'display': {
                               print('This is $arge, subsection,links,display case.');
                               break;
                               }
                           }
                   }
               }
       }
   }
?>
i luv spam
25-Apr-2003 11:46
Noticed some odd switch behavior worth mentioning:

Switching on a variable set as $var="08" and forgetting the quotes within the case results in different behavior depending on the two digit number the variable is set to.

For "01" to "07", using a case like
  case 01:
the case is triggered.

For "08" or "09" the case is skipped.

For "10" to "12" the case is triggered.

Looks like something octal may be going on.

Anyway, not a problem once the case is changed to:
  case "08":
as it should have been from the start.  Just odd.
jason at devnetwork dot net
24-Mar-2003 02:51
It should be pointed out that this:

<?php

$var = 0;

switch ( $var )
{
   case "something":
       $foo = "Broken";
       break;
   default:
       $foo = "Okay";
       break;
}

echo $foo;

?>

Will print out "Broken".  It's not broken, because in PHP, when an Integer and a String are compared, the string is == 0.  So 0 == "something".  However, this is not apparent.  switch() does not do type checking.
kriek at jonkriek dot com
04-Mar-2003 06:13
Nice, clean, template style navigation. In most cases it is fifteen percent faster to use switch/case/break instead of if/elseif/else. Of course this depends on your application and individual code results do very.

<?php
   switch ($_GET['go']) {
       case "1": $inc = 'Page01.php';
       break;
       case "2": $inc = 'Page02.php';
       break;
       case "3": $inc = 'Page03.php';
       break;
       case "4": $inc = 'Page04.php';
       break;
       default: $inc = 'Page01.php';
       break;
   }
   include ($inc);
?>
jemore at m6net dotdot fr
14-Feb-2003 04:26
siwtch() made always a type conversion before comparing all the case value (PHP4.3.0), so the following statement
<?php
     // $a = 'abc0' or 'abc1' or 'abc2', so this is a string
     switch ($a)
     {
       case 'abc0' : $nb += 1; break;
       case 'abc1' : $nb += 2; break;
       case 'abc2' : $nb += 3; break;
     }
?>
is slower than the following statement
<?
     if ($a === 'abc0') $nb += 1;
     elseif ($a === 'abc1') $nb += 2;
     elseif ($a === 'abc2') $nb += 3;
?>
because the '===' (3 equals signs) compare value without type conversion. Using a if/elseif/elseif structure instead of switch/case/case can be 2 times faster (I have made a test)
rmunn at pobox dot com
23-Jan-2003 11:21
In answer to njones at fredesign dot com, what you're seeing is the way the switch statement is supposed to work. The switch statement evaluates the cases, top to bottom, until it finds the first one that matches the value being switch()ed on. So, for example, if you had:

<?php
switch(2) {
case 1: echo "One\n"; break;
case 2: echo "Two\n"; break;
case 3: echo "Three\n"; break;
case 2: echo "Two again\n"; break;
}
?>

Only "Two" would get echoed. "Two again" would NOT get echoed, because once the first case matches, the rest of them do NOT get evaluated. As soon as a matching case is found, the statements starting at that case get executed until the first break, then control flows out the bottom of the switch block.
theonly dot mcseven at gmx dot net
18-Jan-2003 08:44
working a bit around with it I found out that it is not possible to
compare the variable with two different values in one step like this
(system running a w2k server, apache2.0.43 & php430):

<?php
switch ($myvar) {
 case ("foo" || "bar"): //do something
 break;
 case ("other"): //do another thing
 break;
 default:
}
?>

rather use:

<?php
switch ($myvar) {
 case ("foo"):
 case ("bar"): //do something
 break;
 case ("other"): //do another thing
 break;
 default:
}
?>
turk162 at ALLSPAM_hotmail dot com
03-Dec-2002 04:55
On PHP V4.2.1, running on IIS5 as a CGI, I found an anomaly with how SWITCH handled strings.  I've heard that this problem doesn't exist on V4.2.3 on Apache.

This snippet took the wrong branch:

<?PHP
$wonum = '20010E0';
SWITCH ($wonum):
   CASE '20010D0';
     ECHO "<BR>Branching at D with wonum: " . $wonum;
     BREAK;
   CASE '20010E0';
     ECHO "<BR>Branching at E with wonum: " . $wonum;
     BREAK;
ENDSWITCH;
?>

Type casting with $wonum = (STRING) '20010E0'; didn't help.
Changing the order of the CASEs made no difference (it shouldn't, but...)

What did work was using MD5 to force a string comparison:

<?PHP
$wonum = MD5('20010E0');
SWITCH ($wonum):
   CASE MD5('20010D0');
     ECHO "<BR>Branching at D with wonum: " . $wonum;
     BREAK;
   CASE MD5('20010E0');
     ECHO "<BR>Branching at E with wonum: " . $wonum;
     BREAK;
ENDSWITCH;
?>

Moral: test test test
hexa at h3xa dot com
13-Nov-2002 07:55
this is a simple function that returns a random string and uses
switch to determine what kind of string you want.
function r( [string prefix][,int type,][,int chars] );

type = 1 -> only numbers
type = 2 -> only letters
type = 3 -> both

<?php
function r($prefixo = "",$tipo = 3,$numcaracteres = 10) {
   switch ($tipo) {
       case 1:
           for ($x = 1; $x <= $numcaracteres; $x++) {
               $rnum .= chr(rand(48,57));
           }
           return $prefixo . $rnum;
           break;
       case 2:
           for ($x = 1; $x <= $numcaracteres; $x++) {
               if (rand(1,2) == 1) { $rletras .= chr(rand(65,90)); }
               else { $rletras .= chr(rand(97,122)); }
           }
           return $prefixo . $rletras;
           break;
       case 3:
           for ($x = 1; $x <= $numcaracteres; $x++) {
               $r = rand(1,3);
               if ($r == 1) { $rstring .= chr(rand(65,90)); }
               elseif ($r == 2) { $rstring .= chr(rand(97,122)); }
               else { $rstring .= chr(rand(48,57)); }
           }
           return $prefixo . $rstring;
           break;
   }
}
?>
chernyshevsky at hotmail dot com
28-May-2002 03:45
Be very careful when you're using text strings as cases. If the variable supplied to switch() is an integer, the cases would be converted to integer before the comparison is made (usually to zero). The following snippet prints "hello".

<?php
$a = 0;
switch($a) {
 case 'Hello': echo "Hello";
 break;
 }
?>
paz at spiralon dot com
15-May-2002 07:44
In case : ) it helps someone, I was able to clean up some hairball code by using nested switches (didn't see it mentioned here).  Thanks to all those who are writing examples - I love this site!

<?php
$string_match="second";
switch ($string_match) {
case "first":
case "second":
case "third":
   print "<H3>Something for all three</H3><br>";
   switch ($string_match) {
     case "first":
     print "something for first only";
     break;
     case "second":
     case "third":
     print "something for the other two";
     break;
   }
break;
default:
print "<H3>no match</H3>";
}
?>
gray dot quinn at catch-e dot com dot au
21-Mar-2002 10:00
To get the conditional statement to work for the above example use this:

<?php
$chr = substr($a,$i,1);
switch (TRUE) {

case $chr == "" || $chr == "" || $chr == "" || $chr == "":
$a = str_replace(substr($a,$i,1),"a",$a);
break;

case $chr == "" || $chr == "" || $chr == "":
$a = str_replace(substr($a,$i,1),"e",$a);
break;
?>

}
PeterC at (spamme)rm-rfsplat dot com
06-Feb-2002 12:55
Along the lines of using expressions in switch statements.  I came across some code which wrapped switch statements in 'if' blocks like so...
if (isset($var) {
   switch($var) {
       ....
  

But I found the following a little cleaner.

switch ( isset($var) ? $var : defaultValue ) {
...
x@x
25-Jul-2001 02:29
often you will have to perform multiple actions in sequence, but this sequence must be broken once one of them detects a stop condition (such as an error, when validating form request variables).
One way is to use:

if (check1()
&& check2()
&& check3()
) valid();
else error();

But when the sequence is long and must reordered, this can be errorprone because not all line of check have the same syntax (imagine that you want to comment one of them).

Another way is to rewrite it as:

check1() and
check2() and
check3() and
...
valid() or
error();

The above syntax does not fit well when the valid() code must be several statements.
An alternative syntax can be:

switch (false) {
case check1():
case check2():
case check3():
error();
break;
default:
valid();
}

This last equivalent sample show you that each case expressions is evaluated, until one of them evaluates to a value equal (==) to the switch expression. Above, the error() code will only be called if one of the check evaluates to false. And the valid() code will only be evaluated only if the switch reach the default, which means that none of the above check returned false...
bensphpnetemail at supernaut dot org
29-Jun-2001 11:14
It's obvious, but might still bear explicit mention that you can conditionally execute the BREAK statement in order to allow a CASE to fall through to the next CASE. 

e.g.:-> Here, CASE 1 will fall through and the DEFAULT CASE statements will also be executed unless $somevar is true.

<?php
switch ($i) {
   case 0:
       print "i equals 0";
       break;
   case 1:
       print "i equals 1";
       if ($somevar) {
             break;
             }
   default;
       echo 'Some Default Statements';
       break;
}
?>

Cheers,
Ben Nardone
rtreat2 at tampabay dot rr dot com
30-Mar-2001 03:34
just a further example of the above note, you can do the following type of searching:

<?php
switch (true){
   case ( ereg ("stats",$userfile_name) ):
       echo "processing stats";
       process_stats();
       break; 
   case ( ereg("prices",$userfile_name) ):
       echo "processing prices";
       process_prices();
       break; 
   default:
       echo = "File not recognized!!.";
}
?>

this script could be used to determine data formats for uploaded files based on a nameing conve
ntion. just one example.
nospam at please dot com
14-Nov-2000 05:18
Just a trick I have picked up:

If you need to evaluate several variables to find the first one with an actual value, TRUE for instance. You can do it this was.

There is probably a better way but it has worked out well for me.

switch (true) {

  case (X != 1):

  case (Y != 1):

  default:
}

<continuedeclare>
 Last updated: Tue, 15 Nov 2005