6

I have to execute multiple set of instructions based upon a value, for example.

$value = 'AA';
switch ($value) {
    case 'AA':
        echo "value equals  1";
    continue;
    case 'BB':
        echo "value equals 2";
    continue;
    case 'CC' || 'AA':
        echo "value equals 3";
    break;
}

What i am expecting from the above code is it should execute multiple cases based upon the values passed, the variable $value contains AA as the value so hence i am expecting it to execute both

case 'AA' and
case 'CC' || 'AA'

so it should print out value equals 1 value equals 3 however it does not execute it that way i am getting only value equals 1 as output. and if i remove continue from the statement it executes all three cases which is logically wrong. does the PHP's switch statement support multiple cases to be executed based on a single value? is there any workaround for this?

thank you..

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6 Answers 6

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12

When a break is missing then a switch statement enables falling through to the next condition:

$value = 'AA';
switch ($value) {
    case 'AA':
        echo "value equals  1"; // this case has no break, enables fallthrough
    case 'CC':
        echo "value equals 3"; // this one executes for both AA and CC
    break;
    case 'BB':
        echo "value equals 2";
    break;
}
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6 Comments

oh ok, so there is no way switch statement supports executing multiple cases based upon the condition.? if it allows fallthrough if it finds no break then isn't it supposed to check the next case condition and based upon it allow or jumpthough another condition?
@Ibrahim Azhar Armar: Multiple cases can be executed, by arranging the fallthrough structure and conditions accordingly. Actually my first example was a bit off, try the current one - it executes multiple cases for AA.
What exactly is the difference in behaviour now? It looks like it should the same if the first case falls through and the next case checks only CC. Isn't the condition completely ignored on a fall through?
yes kapep. this will not work unless i structure the value accordingly. for example if the value is passed out of context it will still execute the middle case. try assigning DD to $value which is out of context and it will execute the middle case. whereas i expect the code not to run at all if the value passed is out of context.
@Ibrahim Azhar Armar: Actually @kapep unwittingly pointed out a bug which my previous update introduced. ||-ing two non-zero literals always results true, hence it matches every non-zero $value. Which makes the expression meaningless, one could replace case 'AA' || 'CC' with case true and have identical behaviour. At any rate, I rolled back the previous change. Fallthrough multiple execution depends only on the ordering of breakless cases. Value expressions serve only as initial entry points.
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3

The switch statement needs literals in the case blocks. Use an if statements instead.

You can use other sorts of loop to iterate through the value, and then use IF's for comparison. Doing comparison/condition checking isn't possible in the switch cases.

One way to accomplish what you want to do is like this (note IF is being used):

$value = 'AA';
switch($value)
{
    case ('AA'):
        echo "value equals 1<br />";
    case ('BB'):
        if ($value == 'BB'){
            echo "value equals 2<br />";
        }
    case (('AA') || ('CC')):
        echo "value equals 3<br />";
        break;
}

Outputs:

value equals 1
value equals 3

NOTE:- the above solution isn't right although its outputting what you need its not the right solution and if possible i would recommend avoiding. Your needs can easily be fixed using non-switch/case alternatives.

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Comments

1

The work around is to use a set of if and else if statements. Conditions in case statements are not evaluated.

if($value == 'AA') {
    echo "value equals 1";
}
else if($value == 'CC') {
    echo "value equals 3";
}
else { //Or else if($value == 'BB') if you might add more at some point
    echo "value equals 2";
}

The continue (or break statement) ends each case. If it is omitted, execution will fall through to the next case (which is why all three get executed in your case - it falls through all of them, right to the end. If a continue or break is encountered in a case that has been fallen through to, execution will stop there).

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1 Comment

i cannot use if else because code needs to be executed several times based upon value for example Value AA may execute condition 1 and 3, or condition 1 and 2 and 3 or any one condition. if else will come out once it execute the first one. i guess the only way left out is using multiple if
0

After reading the documentation I see that switch statements can have multiple cases which evaluate true, but not multiple case blocks which evaluate true.

Also, the documentation states that break; and continue; in the scope of a switch are equivalent.

If you leave all break; and continue; statements out, you'll see that they all print regardless of matching. You'll have to use the less cool if/else/ifelse statements for this conundrum.

http://php.net/manual/en/control-structures.switch.php

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4 Comments

That won't work. I had never seen a repeated case in a switch before, so I tried it thinking it was a cool concept. Unfortunately, it only evaluates the first instance, so it only prints value equals 1, but not value equals 3.
sure @Patrick Robert Shea O'Connor . looking fwd for your reply :)
continue in a switch statement doesn't make the switch a loop. Even if it would, without modifing the condition, it would be an endless one.
@kapep that's what I was saying, that a break; and continue; in the scope of a switch are the same thing, that they both break the switch out and end any further processing of statements. A switch or for that matter a if/else are not loops. for/while are loops you can wrap around a if/else or switch.
0

You need to write your code like this When we are checking more than one condition than we need to add conditional statement there.

$value = 'AA';
switch ($value) {
    case 'AA':
        echo "value equals  1";
    continue;
    case 'BB':
        echo "value equals 2";
    continue;
    case $value == 'CC' || $value=='AA':
        echo "value equals 3";
    break;
}

Or you can simply write your code in this format (put two different cases for that)

$value = 'AA';
switch ($value) {
    case 'AA':
        echo "value equals  1";
    continue;
    case 'BB':
        echo "value equals 2";
    continue;
    case 'CC':
    case 'AA':
        echo "value equals 3";
    break;
}
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Comments

-2 
$value = 'AA';
switch ($value) {
    case 'AA':
        echo "value equals 1";
        echo "value equals 3";
    break;
    case 'BB':
        echo "value equals 2";
    break;
    case 'CC':
        echo "value equals 3";
    break;
}
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1 Comment

Please add some explanation to your answer such that others can learn from it. As far as I see, you would not run the third case for AA

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