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