PHP's switch statement is suitable for processing multiple fixed value judgments. 1. The switch judges variable values through loose comparison, and has a clear structure, which is suitable for scenarios such as user role, request type, state machine, etc.; 2. Break should be added after each case to avoid penetration, but penetration can also be used to implement multiple cases sharing logic; 3. default is optional but it is recommended to add it to deal with unmatched situations; 4. Pay attention to type matching issues, and manually handle type consistency if necessary.
PHP's switch statement is a very practical control structure, especially suitable for handling multiple fixed value judgments. Compared to writing a bunch of if-else, using switch is more concise and clear.
The basic syntax must be clear
The basic structure of the switch statement is as follows:
switch ($variable) {
case 'value1':
// Execute code break;
case 'value2':
// Execute code break;
default:
// Default} The key point is that each case must be followed by break; otherwise it will "penetrate" to the next case. Sometimes this is the behavior you want, but most of the time it is prone to errors. For example, if you forget to break, the program will continue to execute the next case code, even if it doesn't match.
When is it more appropriate to use switch?
When you face a variable and need to do different processing according to its value, switch is very suitable. Common scenarios include:
- Handle user roles (such as admin, editor, guest)
- Determine the request type (GET, POST, PUT, DELETE)
- Control state machine (such as order status: pending payment, shipped, completed)
In these cases, the value is usually a few fixed options, if-else is written in a verbose way and has poor readability. Use switch to see the corresponding relationship at a glance.
Pay attention to type matching issues
PHP is a weak-type language. Switch uses loose comparisons (==) when comparing, not strict comparisons (===). This may lead to some unexpected results.
For example, the following example:
$var = 0;
switch ($var) {
case '0':
echo "String 0";
break;
case 0:
echo "Integer 0";
break;
}The above code will only output "String 0", because PHP treats integer 0 and string '0' as the same. If you pay special attention to types, you have to make extra judgments in the case or convert the types first.
Small details of default and break
default is optional, recommended to handle situations where there is no match and enhances robustness.
Regarding break, as mentioned earlier, if not added, the next case will continue to be executed. Sometimes this can be taken advantage of, such as multiple cases sharing a piece of logic:
case 'apple':
case 'orange':
case 'banana':
echo "This is fruit";
break;This way of writing means that these three values will trigger the same output, avoiding repeated code writing.
Basically all that is it. If you master these points, switch will be very easy to use.
The above is the detailed content of The PHP Switch Statement. For more information, please follow other related articles on the PHP Chinese website!
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