165 lines
2.5 KiB
Markdown
165 lines
2.5 KiB
Markdown
---
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title: Loop
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localeTitle: 环
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---
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# PHP循环
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当您需要多次重复相同的任务时，您可以使用循环而不是一遍又一遍地添加相同的代码。 在PHP中有以下循环语句：
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* for - 循环遍历具有特定次数的代码块。
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* while - 如果条件为真，则循环遍历代码块。
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* do ... while - 循环遍历代码块1并在条件为真时继续循环。
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* foreach - 循环遍历数组中每个值的代码块。
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在循环中使用`break`可以停止循环执行。
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# 对于循环
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循环遍历具有特定次数的代码块。
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## 句法
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```
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for (init counter; condition; counter increment or decrement)
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{
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// Code to be executed
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}
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```
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## 例
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```php
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<?php
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for($index = 0; $index < 5; $index ++)
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{
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echo "Current loop counter ".$index.".\n";
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}
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?>
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```
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## 产量
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```
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> Current loop counter 0.
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> Current loop counter 1.
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> Current loop counter 2.
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> Current loop counter 3.
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> Current loop counter 4.
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```
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# 循环
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如果条件为真，则循环遍历代码块。
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## 句法
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```
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while (condition)
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{
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// Code to be executed
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}
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```
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## 例
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```php
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<?php
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$index = 10;
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while ($index >= 0)
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{
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echo "The index is ".$index.".\n";
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$index--;
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}
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?>
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```
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## 产量
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```
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> The index is 10.
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> The index is 9.
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> The index is 8.
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> The index is 7.
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> The index is 6.
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> The index is 5.
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> The index is 4.
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> The index is 3.
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> The index is 2.
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> The index is 1.
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> The index is 0.
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```
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# 做......循环
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循环遍历代码块1并在条件为真时继续循环。
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## 句法
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```
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do
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{
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// Code to be executed
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}
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while (condition);
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```
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## 例
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```php
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<?php
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$index = 3;
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do
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{
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// execute this at least 1 time
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echo "Index: ".$index.".\n";
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$index --;
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}
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while ($index > 0);
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?>
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```
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## 产量
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```
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> Index: 3.
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> Index: 2.
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> Index: 1.
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```
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# Foreach循环
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循环遍历数组中每个值的代码块。
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## 句法
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```
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foreach ($array as $value)
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{
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// Code to be executed
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}
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```
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## 例
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```php
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<?php
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$array = ["Ali", "Ah Kao", "Muthu", "Gwen", "Lucida", "Cecily", "Arthur", "Flora"];
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foreach ($array as $name)
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{
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echo "Hi, my name is ".$name.".\n";
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if ($name == "Cecily")
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{
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echo "\"Hello, ".$name."!\"";
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// stop the loop if name is Cecily
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break;
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}
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}
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?>
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```
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## 产量
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```
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> Hi, my name is Ali.
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> Hi, my name is Ah Kao.
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> Hi, my name is Muthu.
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> Hi, my name is Gwen.
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> Hi, my name is Lucida.
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> Hi, my name is Cecily.
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> "Hello, Cecily!"
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``` |