117 lines
1.6 KiB
Markdown
117 lines
1.6 KiB
Markdown
---
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title: Learn About Php Loops
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localeTitle: 了解Php循环
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---
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循环是执行指定次数的代码块。使用循环减少了代码行数。
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PHP适用于4种不同类型的循环：
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* 循环
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* 做... while循环
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* 对于循环
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* Foreach循环
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## 循环
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只要指定的条件为真， `while`循环就会继续执行。
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\`PHP
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```
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Example:
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```php
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<?php
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$x = 1;
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while($x <= 3)
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{
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echo "x=$x ";
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$x++;
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}
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?>
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```
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```
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Output:
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x=1 x=2 x=3
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```
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## Do...while loop
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In the `do...while` loop the block of code is executed before the condition is checked.
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```php
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<?php
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do {
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execute code;
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} while (condition);
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?>
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```
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Example:
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```php
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<?php
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$x= 1;
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do {
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echo "x=$x ";
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$x++;
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} while ($x < 5);
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?>
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```
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```
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Output:
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x=1 x=2 x=3 x=4
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```
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## For loop
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The `for` loop is used when the number of times the block is to be executed is known in advance.
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```php
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<?php
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for (variable initialisation; test condition; increment)
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{
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execute code;
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}
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?>
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```
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Example:
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```php
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<?php
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for ($x=1 ; $x <= 4 ; $x++)
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{
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echo "x= $x ";
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}
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?>
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```
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```
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Output:
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x=1 x=2 x=3 x=4
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```
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## Foreach loop
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The `foreach` loop helps in traversing through arrays.
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```php
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<?php
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foreach ($array as $value)
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{
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executable code;
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}
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?>
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```
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Example:
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```php
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<?php
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$numbers= array("One", "Two", "Three");
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foreach ($numbers as $value)
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{
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echo "$value ";
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}
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?>
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```
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```
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Output:
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One Two Three
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``` |