PHP 8.2.0 Alpha 2 available for testing

switch

(PHP 4, PHP 5, PHP 7, PHP 8)

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.

Note: 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.

Note:

Note that switch/case does loose comparison.

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:

Example #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;
}
?>

Example #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 whose expression evaluates to 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. 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";
}
?>

Note: Multiple default cases will raise a E_COMPILE_ERROR error.

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;
?>

It's possible to use a semicolon instead of a colon after a case like:

<?php
switch($beer)
{
    case 
'tuborg';
    case 
'carlsberg';
    case 
'heineken';
        echo 
'Good choice';
        break;
    default;
        echo 
'Please make a new selection...';
        break;
}
?>

add a note add a note

User Contributed Notes 6 notes

up
269
MaxTheDragon at home dot nl
10 years ago
This is listed in the documentation above, but it's a bit tucked away between the paragraphs. The difference between a series of if statements and the switch statement is that the expression you're comparing with, is evaluated only once in a switch statement. I think this fact needs a little bit more attention, so here's an example:

<?php
$a
= 0;

if(++
$a == 3) echo 3;
elseif(++
$a == 2) echo 2;
elseif(++
$a == 1) echo 1;
else echo
"No match!";

// Outputs: 2

$a = 0;

switch(++
$a) {
    case
3: echo 3; break;
    case
2: echo 2; break;
    case
1: echo 1; break;
    default: echo
"No match!"; break;
}

// Outputs: 1
?>

It is therefore perfectly safe to do:

<?php
switch(winNobelPrizeStartingFromBirth()) {
case
"peace": echo "You won the Nobel Peace Prize!"; break;
case
"physics": echo "You won the Nobel Prize in Physics!"; break;
case
"chemistry": echo "You won the Nobel Prize in Chemistry!"; break;
case
"medicine": echo "You won the Nobel Prize in Medicine!"; break;
case
"literature": echo "You won the Nobel Prize in Literature!"; break;
default: echo
"You bought a rusty iron medal from a shady guy who insists it's a Nobel Prize..."; break;
}
?>

without having to worry about the function being re-evaluated for every case. There's no need to preemptively save the result in a variable either.
up
92
septerrianin at mail dot ru
3 years ago
php 7.2.8.
The answer to the eternal question " what is faster?":
1 000 000 000 iterations.

<?php
$s
= time();
for (
$i = 0; $i < 1000000000; ++$i) {
 
$x = $i%10;
  if (
$x == 1) {
   
$y = $x * 1;
  } elseif (
$x == 2) {
   
$y = $x * 2;
  } elseif (
$x == 3) {
   
$y = $x * 3;
  } elseif (
$x == 4) {
   
$y = $x * 4;
  } elseif (
$x == 5) {
   
$y = $x * 5;
  } elseif (
$x == 6) {
   
$y = $x * 6;
  } elseif (
$x == 7) {
   
$y = $x * 7;
  } elseif (
$x == 8) {
   
$y = $x * 8;
  } elseif (
$x == 9) {
   
$y = $x * 9;
  } else {
   
$y = $x * 10;
  }
}
print(
"if: ".(time() - $s)."sec\n");

$s = time();
for (
$i = 0; $i < 1000000000; ++$i) {
 
$x = $i%10;
  switch (
$x) {
  case
1:
   
$y = $x * 1;
    break;
  case
2:
   
$y = $x * 2;
    break;
  case
3:
   
$y = $x * 3;
    break;
  case
4:
   
$y = $x * 4;
    break;
  case
5:
   
$y = $x * 5;
    break;
  case
6:
   
$y = $x * 6;
    break;
  case
7:
   
$y = $x * 7;
    break;
  case
8:
   
$y = $x * 8;
    break;
  case
9:
   
$y = $x * 9;
    break;
  default:
   
$y = $x * 10;
  }
}
print(
"switch: ".(time() - $s)."sec\n");
?>

Results:
if: 69sec
switch: 42sec
up
99
nospam at please dot com
21 years ago
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:
}
up
9
none at example dot com
2 years ago
A note on continue, continue 2, and break:

$a = [1, 2, 3];

foreach($a as $b) {
  switch($b) {
    case 1:
      echo 'a'; continue;
    case 2:
      echo 'b'; continue;
    default:
      echo 'c'; continue;
  }

  echo '0';
}
// outputs a0b0c0 (and warns twice about continue in a switch statement)

foreach($a as $b) {
  switch($b) {
    case 1:
      echo 'a'; break;
    case 2:
      echo 'b'; break;
    default:
      echo 'c'; break;
  }

  echo '0';
}
// outputs a0b0c0

foreach($a as $b) {
  switch($b) {
    case 1:
      echo 'a'; continue 2;
    case 2:
      echo 'b'; continue 2;
    default:
      echo 'c'; continue 2;
  }

  echo '0';
}
//outputs abc0

In short, continue and break will more or less behave the same (albeit the former throws out warnings), but continue 2 will end the loop iteration, and move to the next iteration (even if there is a block in the iteration after the switch statement).
up
14
Hayley Watson
14 years ago
Something not mentioned in the documentation itself, and only touched on momentarily in these notes, is that the default: case need not be the last clause in the switch.
<?php
for($i=0; $i<8; ++$i)
{
    echo
$i,"\t";
    switch(
$i)
    {
    case
1: echo "One"; break;
    case
2:
    default: echo
"Thingy"; break;
    case
3:
    case
4: echo "Three or Four"; break;
    case
5: echo "Five"; break;
    }
    echo
"\n";
}
?>
Outputs what you'd expect, namely
0       Thingy
1       One
2       Thingy
3       Three or Four
4       Three or Four
5       Five
6       Thingy
7       Thingy
with case 2 and the default both producing the same result ("Thingy"); strictly speaking, the case 2 clause is completely empty and control just falls straight through. The same result could have been achieved with
<?php
switch($i)
{
    case
1: echo "One"; break;
    case
3:
    case
4: echo "Three or Four"; break;
    case
5: echo "Five"; break;
    default: echo
"Thingy"; break;
}
?>
But if "case 2" represented a fairly common case (other than "everything else"), then it would be better to declare it explicitly, not only because it saves time by not having to test EVERY other case first  (in the current example, PHP finds 'case 2' in the first switch in two tests, but in the second switch it has to make four tests before giving up and going with the default) but also because someone (perhaps yourself in a few months' time) will be reading the code and expecting to see it handled. Listing it explicitly aids comprehension
up
1
chernyshevsky at hotmail dot com
20 years ago
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;
}
?>
To Top