PHP Control Structures switch


The switch structure performs the same function as a series of if statements, but can do the job in fewer lines of code. The value to be tested, as defined in the switch statement, is compared for equality with the values in each of the case statements until a match is found and the code in that block is executed. If no matching case statement is found, the code in the default block is executed, if it exists.

Each block of code in a case or default statement should end with the break statement. This stops the execution of the switch structure and continues code execution immediately afterwards. If the break statement is omitted, the next case statement's code is executed, even if there is no match. This can cause unexpected code execution if the break statement is forgotten, but can also be useful where multiple case statements need to share the same code.

switch ($colour) {
case "red":
    echo "the colour is red";
case "green":
case "blue":
    echo "the colour is green or blue";
case "yellow":
    echo "the colour is yellow";
    // note missing break, the next block will also be executed
case "black":
    echo "the colour is black";
    echo "the colour is something else";

In addition to testing fixed values, the construct can also be coerced to test dynamic statements by providing a boolean value to the switch statement and any expression to the case statement. Keep in mind the first matching value is used, so the following code will output "more than 100":

$i = 1048;
switch (true) {
case ($i > 0):
    echo "more than 0";
case ($i > 100):
    echo "more than 100";
case ($i > 1000):
    echo "more than 1000";

For possible issues with loose typing while using the switch construct, see Switch Surprises