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PHP - Switch Statement

The switch statement in PHP can be treated as an alternative to a series of if…else statements on the same expression. Suppose you need to compare an expression or a variable with many different values and execute a different piece of code depending on which value it equals to. In such a case, you would use multiple if…elseif…else constructs.

However, such a construct can make the code quite messy and difficult to follow. To simplify such codes, you can use the switch case construct in PHP that offers a more compact alternative to avoid long blocks of if..elseif..else codes.

The following PHP script uses if elseif statements −

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

You can get the same result by using the switch case statements as shown below −

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

The switch statement is followed by an expression, which is successively compared with value in each case clause. If it is found that the expression matches with any of the cases, the corresponding block of statements is executed.

  • The switch statement executes the statements inside the curly brackets line by line.

  • If and when a case statement is found whose expression evaluates to a value that matches the value of the switch expression, PHP starts to execute the statements until the end of the switch block, or the first time it encounters 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.

Example

Try to run the above code by removing the breaks. If the value of x is 0, you’ll find that the output includes "x equals 1" as well as "x equals 2" lines.

<?php
   $x=0;
   switch ($x) {
      case 0:
         echo "x equals 0 \n";
      case 1:
         echo "x equals 1 \n";
      case 2:
         echo "x equals 2";
   }
?>

It will produce the following output −

x equals 0
x equals 1
x equals 2

Thus, it is important make sure to end each case block with a break statement.

The Default Case in Switch

A special case is the default case. This case matches anything that wasn't matched by the other cases. Using default is optional, but if used, it must be the last case inside the curly brackets.

You can club more than one cases to simulate multiple logical expressions combined with the or operator. 

<?php
   $x=10;
   switch ($x) {
      case 0:
      case 1:
      case 2:
         echo "x between 0 and 2 \n";
      break;
      default:
         echo "x is less than 0 or greater than 2";
   }
?>

The values to be compared against are given in the case clause. The value can be a number, a string, or even a function. However you cannot use comparison operators (<, > == or !=) as a value in the case clause.

You can choose to use semicolon instead of colon in the case clause. If no matching case found, and there is no default branch either, then no code will be executed, just as if no if statement was true.

The switch-endswitch Statement

PHP allows the usage of alternative syntax by delimiting the switch construct with switch-endswitch statements. The following version of switch case is acceptable.

<?php
   $x=0;
   switch ($x) :
      case 0:
         echo "x equals 0";
      break;
      case 1:
         echo "x equals 1 \n";
      break;
      case 2:
         echo "x equals 2 \n";
      break;
      default:
         echo "None of the above";
   endswitch
?>

Using the Break Statement in Switch…Case

Obviously, you needn’t write a break to terminate the default case, it being the last case in the switch construct.

Example

Take a look at the following example −

<?php
   $d = date("D");

   switch ($d){
      case "Mon":
         echo "Today is Monday";
      break;

      case "Tue":
         echo "Today is Tuesday";
      break;
	  
      case "Wed":
         echo "Today is Wednesday";
      break;

      case "Thu":
         echo "Today is Thursday";
      break;

      case "Fri":
         echo "Today is Friday";
      break;

      case "Sat":
         echo "Today is Saturday";
      break;

      case "Sun":
         echo "Today is Sunday";
      break;

      default:
         echo "Wonder which day is this ?";
   }
?>

It will produce the following output −

Today is Monday
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