php中用foreach来操作数组的代码

　　foreach()有两种用法：
复制代码 代码如下:
foreach(array_name as $value)
{
statement;
}

这里的array_name是你要遍历的数组名，每次循环中，array_name数组的当前元素的值被赋给$value,并且数组内部的下标向下移一 步，也就是下次循环回得到下一个元素。
复制代码 代码如下:
foreach(array_name as $key => $value)
{
statement;
}

这里跟第一种方法的区别就是多了个$key,也就是除了把当前元素的值赋给$value外，当前元素的键值也会在每次循环中被赋给变量$key。键值可以 是下标值，也可以是字符串。比如book[0]=1中的0，book[id]=001中的id.
程序实例1：
复制代码 代码如下:
<?php
/*-------------------------------------------------------------------------*/
/* foreach example 1: value only */
echo foreach example 1: value only .<br />;
$a = array(1, 2, 3, 17);
foreach ($a as $v) {
echo Current value of .$a.:. $v.<br />;
}
?>
// 运行结果
foreach example 1: value only
Current value of $a: 1
Current value of $a: 2
Current value of $a: 3
Current value of $a: 17

2
复制代码 代码如下:
/*-------------------------------------------------------------------------*/
/* foreach example 2: value (with key printed for illustration) */
echo <br />.<br />.foreach example 2: value (with key printed for illustration) .<br />;
$a = array(1, 2, 3, 17);
$i = 0; /* for illustrative purposes only */
foreach ($a as $v) {
echo $a[$i] => $v.<br />;
$i++;
}
// 程序运行结果
foreach example 2: value (with key printed for illustration)
$a[0] => 1
$a[1] => 2
$a[2] => 3
$a[3] => 17

3
复制代码 代码如下:
/*-------------------------------------------------------------------------*/
/* foreach example 3: key and value */
echo <br />.<br />.foreach example 3: key and value .<br />;
$a = array(
one => 1,
two => 2,
three => 3,
seventeen => 17
);
foreach ($a as $k => $v) {
echo $a[$k] => $v.<br />;
}
// 程序运行结果
foreach example 3: key and value
$a[one] => 1
$a[two] => 2
$a[three] => 3
$a[seventeen] => 17

4
复制代码 代码如下:
/*-------------------------------------------------------------------------*/
/* foreach example 4: multi-dimensional arrays */
echo <br />.<br />.foreach example 4: multi-dimensional arrays .<br />;
$a = array();
$a[0][0] = a;
$a[0][1] = b;
$a[1][0] = y;
$a[1][1] = z;
foreach ($a as $v1) {
foreach ($v1 as $v2) {
echo $v2n;
}
}
// 程序运行结果
foreach example 4: multi-dimensional arrays
a b y z

5
复制代码 代码如下:
/*-------------------------------------------------------------------------*/
/* foreach example 5: dynamic arrays */
echo <br />.<br />.foreach example 5: dynamic arrays .<br />;
foreach (array(1, 2, 3, 4, 5) as $v) {
echo $vn;
}
// 程序运行结果
foreach example 5: dynamic arrays
1 2 3 4 5

也可以这么用：
复制代码 代码如下:
$messageNav[首页] =ROOT_PATH;
$messageNav[人才交流] =#
$messageNav[动态专栏] =hragent/cn/
<?php $i = 0;foreach ($messageNav as $key=>$value):?>
<?php if ($i != count($messageNav) - 1):?>
<a href=<?=$value?>><?=$key?></a>>
<?php else:?>
<a href=<?=$value?> class=onlink><?=$key?></a>
<?php endif;?>
<?php $i++;endforeach;?>