php中foreach()函数的用法

转自：http://zhanglulu33.blog.163.com/blog/static/112799542010027115254461/

foreach()有两种用法：1： 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。2：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”.

示范用法的更多例子：

<?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 />';

}

/*-------------------------------------------------------------------------*/

/* 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++;

}

/*-------------------------------------------------------------------------*/

/* 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 />';

}

/*-------------------------------------------------------------------------*/

/* 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 "$v2"n";

}

}

/*-------------------------------------------------------------------------*/

/* foreach example 5: dynamic arrays */

echo '<br />'.'<br />'."foreach example 5: dynamic arrays ".'<br />';

foreach (array(1, 2, 3, 4, 5) as $v) {

echo "$v"n";

}

?>

结果如下:

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

foreach example 2: value (with key printed for illustration)

$a[0] => 1

$a[1] => 2

$a[2] => 3

$a[3] => 17

foreach example 3: key and value

$a[one] => 1

$a[two] => 2

$a[three] => 3

$a[seventeen] => 17

foreach example 4: multi-dimensional arrays

a b y z

foreach example 5: dynamic arrays

1 2 3 4 5