switch

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# `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.

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

    if ($i == 0) {
        print "i equals 0";
    }
    if ($i == 1) {
        print "i equals 1";
    }
    if ($i == 2) {
        print "i equals 2";
    }

    switch ($i) {
        case 0:
            print "i equals 0";
            break;
        case 1:
            print "i equals 1";
            break;
        case 2:
            print "i equals 2";
            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:

    switch ($i) {
        case 0:
            print "i equals 0";
        case 1:
            print "i equals 1";
        case 2:
            print "i equals 2";
    }

Here, if $i is equal to 0, PHP would execute all of the print statements! If $i is equal to 1, PHP would execute the last two print 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.

    switch ($i) {
        case 0:
        case 1:
        case 2:
            print "i is less than 3 but not negative";
            break;
        case 3:
            print "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:

    switch ($i) {
        case 0:
            print "i equals 0";
            break;
        case 1:
            print "i equals 1";
            break;
        case 2:
            print "i equals 2";
            break;
        default:
            print "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 .

    switch ($i):
        case 0:
            print "i equals 0";
            break;
        case 1:
            print "i equals 1";
            break;
        case 2:
            print "i equals 2";
            break;
        default:
            print "i is not equal to 0, 1 or 2";
    endswitch;

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