freeCodeCamp/guide/chinese/miscellaneous/learn-about-php-loops/index.md

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Learn About Php Loops	了解Php循环

循环是执行指定次数的代码块。使用循环减少了代码行数。

PHP适用于4种不同类型的循环：

• 循环
• 做... while循环
• 对于循环
• Foreach循环

循环

只要指定的条件为真， while循环就会继续执行。

`PHP

Example: 
 ```php 
 <?php 
  $x = 1; 
   while($x <= 3) 
   { 
     echo "x=$x "; 
     $x++; 
   } 
 ?> 

Output: 
x=1 x=2 x=3 

Do...while loop

In the do...while loop the block of code is executed before the condition is checked.

<?php 
   do { 
     execute code; 
   } while (condition); 
?> 

Example:

<?php 
$x= 1; 
   do { 
     echo "x=$x "; 
     $x++; 
   } while ($x < 5); 
?> 

Output: 
x=1 x=2 x=3 x=4 

For loop

The for loop is used when the number of times the block is to be executed is known in advance.

<?php 
   for (variable initialisation; test condition; increment) 
   { 
     execute code; 
   } 
?> 

Example:

<?php 
  for ($x=1 ; $x <= 4 ; $x++) 
  { 
    echo "x= $x "; 
  } 
?> 

Output: 
x=1 x=2 x=3 x=4 

Foreach loop

The foreach loop helps in traversing through arrays.

<?php 
  foreach ($array as $value) 
  { 
    executable code; 
  } 
?> 

Example:

<?php 
$numbers= array("One", "Two", "Three"); 
 foreach ($numbers as $value) 
 { 
   echo "$value "; 
 } 
?> 

Output: 
One Two Three