PHP Switch

PHP Switch Statement: A Comprehensive Guide

The PHP switch statement is a useful tool for controlling the flow of code in a program. This statement allows you to test a single expression against multiple possible values, and execute different code based on the result. In this article, we will cover everything you need to know about the PHP switch statement, including how to use it, common uses, and best practices. （PHP switch语句是用于控制程序中代码流的有用工具。此语句允许您针对多个可能的值测试单个表达式，并根据结果执行不同的代码。在本文中，我们将介绍您需要了解的有关PHP switch语句的所有信息，包括如何使用它、常见用途和最佳实践。）

How to Use the PHP Switch Statement #

How to Use the PHP Switch Statement （如何使用PHP Switch语句）

The basic syntax of a PHP switch statement is as follows:

switch (expression) {
   case value1:
       // code to be executed if expression = value1
（//表达式= value1时执行的代码）
       break;
   case value2:
       // code to be executed if expression = value2
（//表达式= value2时执行的代码）
       break;
   ...
（那些家伙是不会放我们走的）
   default:
       // code to be executed if expression does not match any values
}

The expression is evaluated once, and its value is compared to each of the values in the case statements. If a match is found, the code associated with that case is executed. If no match is found, the code in the default block is executed. （表达式计算一次，并将其值与case语句中的每个值进行比较。如果找到匹配项，则执行与该案例相关联的代码。如果未找到匹配项，则执行默认块中的代码。）

Common Uses for the PHP Switch Statement #

Common Uses for the PHP Switch Statement （PHP Switch语句的常见用法）

One of the most common uses for the PHP switch statement is to control the flow of a program based on user input. For example, you could use a switch statement to display different messages based on the value of a form field:

switch ($_POST["field_name"]) {
   case "value1":
       echo "You entered value1.";
       break;
   case "value2":
       echo "You entered value2.";
       break;
   default:
       echo "You entered an unknown value.";
}

Another common use for the PHP switch statement is to control the flow of a program based on the values of multiple variables. For example, you could use a switch statement to perform different calculations based on the values of two variables:

switch ($variable1 . "-" . $variable2) {
   case "value1-valueA":
       // code to be executed if $variable1 = "value1" and $variable2 = "valueA"
（//如果$ variable1 = "value1"和$ variable2 = "valueA"则执行代码）
       break;
   case "value2-valueB":
       // code to be executed if $variable1 = "value2" and $variable2 = "valueB"
（//如果$ variable1 = "value2"且$ variable2 = "valueB"则执行代码）
       break;
   ...
（那些家伙是不会放我们走的）
   default:
       // code to be executed if no match is found
}

Best Practices for the PHP Switch Statement #

Best Practices for the PHP Switch Statement （PHP Switch语句的最佳实践）

• Always include a break statement after each case block, to prevent fall-through. （-始终在每个案例块后面添加break语句，以防止跌倒。）

• Use the default block to handle unexpected values, rather than relying on fall-through. （-使用默认块来处理意外值，而不是依赖于fall-through。）

• Consider using an if-else statement instead of a switch statement if you only need to test a single expression against a few possible values. （-如果您只需要针对几个可能的值测试单个表达式，请考虑使用if-else语句而不是switch语句。）

• Use the switch statement to improve readability and maintainability when testing a single expression against multiple values. （-针对多个值测试单个表达式时，使用switch语句来提高可读性和可维护性。）

Conclusion #

Conclusion （小结）

In conclusion, the PHP switch statement is a useful tool for controlling the flow of code in a program. With its ability to test a single expression against multiple possible values, it can help you simplify complex code and make your programs more readable and maintainable. Whether you are new to PHP or an experienced programmer, understanding how to use the PHP switch statement is an essential part of any PHP developer’s toolkit. （总之， PHP switch语句是控制程序中代码流的有用工具。凭借其针对多个可能值测试单个表达式的能力，它可以帮助您简化复杂的代码，并使您的程序更具可读性和可维护性。无论您是PHP新手还是经验丰富的程序员，了解如何使用PHP switch语句是任何PHP开发人员工具包的重要组成部分。）