php switch 文法用於執行基於不同條件不同的行動。
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開關語句的PHP
使用switch語句來選擇代碼的許多組成部分之一被執行。
文法
switch (n)
{
case label1:
code to be executed if n=label1;
break;
case label2:
code to be executed if n=label2;
break;
default:
code to be executed if n is different from both label1 and label2;
}
這是它的工作原理：首先，我們有一個單一運算式n（常常是一個變數），只計算一次。該運算式的值，然後比較與結構中每個案例的價值觀。如果有匹配，與該案例相關的代碼就會被執行。利用休息時間，避免因進入下一個代碼自動執行。預設語句用於如果沒有找到匹配。
例如
<html>
<body>
<?php
switch ($x)
{
case 1:
echo "Number 1";
break;
case 2:
echo "Number 2";
break;
case 3:
echo "Number 3";
break;
default:
echo "No number between 1 and 3";
}
?>
switch (expression)
{
case label1:
code to be executed if expression = label1;
break;
case label2:
code to be executed if expression = label2;
break;
default:
code to be executed
if expression is different
from both label1 and label2;
}
</body>
</html>
工作原理：
對錶達式（通常是變數）進行一次計算
把運算式的值與結構中 case 的值進行比較
如果存在匹配，則執行與 case 關聯的代碼
代碼執行後，break 語句阻止代碼跳入下一個 case 中繼續執行
如果沒有 case 為真，則使用 default 語句
<?php
switch ($x)
{
case 1:
echo "Number 1";
break;
case 2:
echo "Number 2";
break;
case 3:
echo "Number 3";
break;
default:
echo "No number between 1 and 3";
}
?>
</body>
</html>
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