PHP Switch语句

PHP switch语句用于从多个条件中执行一条语句。它的工作方式类似于PHP的if-else-if语句。

语法

switch(expression){    
case value1:    
 //code to be executed
 break;
case value2:    
 //code to be executed
 break;
......    
default:     
 code to be executed if all cases are not matched;  
}

关于switch case的重要注意事项

1. default 是可选语句。即使不重要，default必须始终是最后一个语句。
2. switch语句中只能有一个 default 。多个default可能导致 致命错误 。
3. 每个case可以有一个 break 语句，用于终止语句序列。
4. 在switch中， break 语句是可选的。如果不使用break，所有与匹配case值相对应的语句都会执行。
5. PHP允许在switch表达式中使用数字、字符、字符串和函数。
6. 允许嵌套switch语句，但会使程序变得更复杂且不易阅读。
7. 你可以使用分号(;)代替冒号(:)，不会产生任何错误。

PHP Switch流程图

PHP Switch 示例

<?php    
num=20;    
switch(num){    
case 10:    
echo("number is equals to 10");    
break;    
case 20:    
echo("number is equal to 20");    
break;    
case 30:    
echo("number is equal to 30");    
break;    
default:    
echo("number is not equal to 10, 20 or 30");    
}   
?>

输出：

number is equal to 20

PHP字符的switch语句

检查元音和辅音的程序

我们将传递一个字符给switch表达式来检查它是元音还是辅音。如果传递的字符是A、E、I、O或U，它将是元音，否则是辅音。

<?php    
    ch = 'U';
    switch (ch)
    {   
        case 'a': 
            echo "Given character is vowel";
            break;
        case 'e': 
            echo "Given character is vowel";
            break;
        case 'i': 
            echo "Given character is vowel";
            break;
        case 'o': 
            echo "Given character is vowel";
            break;  
        case 'u': 
            echo "Given character is vowel";
            break;
        case 'A': 
            echo "Given character is vowel";
            break;
        case 'E': 
            echo "Given character is vowel";
            break;
        case 'I': 
            echo "Given character is vowel";
            break;
        case 'O': 
            echo "Given character is vowel";
            break;
        case 'U': 
            echo "Given character is vowel";
            break;
        default: 
            echo "Given character is consonant";
            break;
    }
?>  

输出：

Given character is vowel

PHP中的字符串 switch 语句

PHP允许在switch表达式中传递字符串。让我们通过在switch case语句中传递字符串来看下面的课程时长示例。

<?php    
    ch = "B.Tech";
    switch (ch)
    {   
        case "BCA": 
            echo "BCA is 3 years course";
            break;
        case "Bsc": 
            echo "Bsc is 3 years course";
            break;
        case "B.Tech": 
            echo "B.Tech is 4 years course";
            break;
        case "B.Arch": 
            echo "B.Arch is 5 years course";
            break;
        default: 
            echo "Wrong Choice";
            break;
    }
?>  

输出：

B.Tech is 4 years course

PHP的switch语句是穿透的

PHP的switch语句是穿透的。这意味着在找到第一个匹配项后，如果没有找到break语句，它将执行所有的语句。

<?php    
    ch = 'c';
    switch (ch)
    {   
        case 'a': 
            echo "Choice a";
            break;
        case 'b': 
            echo "Choice b";
            break;
        case 'c': 
            echo "Choice c";    
            echo "</br>";
        case 'd': 
            echo "Choice d";
            echo "</br>";
        default: 
            echo "case a, b, c, and d is not found";
    }
?>  

输出：

Choice c
Choice d
case a, b, c, and d is not found

PHP嵌套的switch语句

嵌套的switch语句意味着在另一个switch语句内部使用switch语句。有时会导致混淆。

<?php    
    car = "Hyundai";model = "Tucson";  
        switch( car )         {             case "Honda":                 switch(model )   
                {  
                    case "Amaze":  
                           echo "Honda Amaze price is 5.93 - 9.79 Lakh."; 
                        break;  
                    case "City":  
                           echo "Honda City price is 9.91 - 14.31 Lakh.";  
                        break;   
                }  
                break;  
            case "Renault":  
                switch( model )                  {                     case "Duster":                         echo "Renault Duster price is 9.15 - 14.83 L.";
                        break;                     case "Kwid":                            echo "Renault Kwid price is 3.15 - 5.44 L.";
                        break;                 }                 break;             case "Hyundai":                 switch(model )   
                {  
                    case "Creta":  
                        echo "Hyundai Creta price is 11.42 - 18.73 L.";
                        break;  
        case "Tucson":  
                           echo "Hyundai Tucson price is 22.39 - 32.07 L.";
                        break; 
                    case "Xcent":  
                           echo "Hyundai Xcent price is 6.5 - 10.05 L.";
                        break;  
                }  
                break;   
        }
?>  

输出：

Hyundai Tucson price is 22.39 - 32.07 L.