68 lines
1.8 KiB
Markdown
68 lines
1.8 KiB
Markdown
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---
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title: PHP Switch
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localeTitle: PHP开关
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---
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## PHP开关
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PHP中的`switch`语句类似于同一表达式上的一系列`if`语句。 `switch`语句用于在不同条件下执行不同的操作。 `switch`语句的语法如下
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```
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switch (expression) {
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case label1:
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// code block to be executed if there is a match with result of expression
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break;
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case label2:
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// code block to be executed if there is a match with result of expression
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break;
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case label3:
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// code block to be executed if there is a match with result of expression
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break;
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default:
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// code block to be executed if there is no match with result of expression
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}
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```
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当我们运行程序时，将评估`switch`语句中的表达式。如果存在匹配则使用相应的标签检查该表达式的结果，然后执行相应的`case`块。如果未找到任何case语句的匹配项，则仅执行`default`后面的代码块。
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`switch`声明的例证与一个例子的
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```
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<?php
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$i = 1
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switch ($i) {
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case 0:
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echo "i equals 0";
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break;
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case 1:
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echo "i equals 1";
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break;
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case 2:
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echo "i equals 2";
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break;
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}
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?>
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```
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`switch`语句也可以在没有`break`语句的情况下使用。在这种情况下，匹配案例之后的陈述将被执行。下面是没有`break`语句的`switch`语句的用法。
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```
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<?php
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switch ($i) {
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case 0:
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echo "i equals 0";
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case 1:
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echo "i equals 1";
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case 2:
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echo "i equals 2";
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}
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?>
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/*output --> i equals 0i equals 1i equals 2 */
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```
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#### 更多信息：
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[Switch语句 - PHP文档](http://php.net/manual/en/control-structures.switch.php)
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[PHP5 Switch - W3Schools](https://www.w3schools.com/php/php_switch.asp)
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