php中foreach()函数的用法

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：
/*-------------------------------------------------------------------------*/
/* foreach example 1: value only */
echo "foreach example 1: value only ".'
';
$a = array(1, 2, 3, 17);
foreach ($a as $v) {
   echo "Current value of "$a: $v".'
';
}
/*-------------------------------------------------------------------------*/
/* foreach example 2: value (with key printed for illustration) */
echo '
'.'
'."foreach example 2: value (with key printed for illustration) ".'
';
$a = array(1, 2, 3, 17);
$i = 0; /* for illustrative purposes only */
foreach ($a as $v) {
    echo ""$a[$i] => $v".'
';
    $i++;
}
/*-------------------------------------------------------------------------*/
/* foreach example 3: key and value */
echo '
'.'
'."foreach example 3: key and value ".'
';
$a = array(
    "one" => 1,
    "two" => 2,
    "three" => 3,
    "seventeen" => 17
);
foreach ($a as $k => $v) {
    echo ""$a[$k] => $v".'
';
}
/*-------------------------------------------------------------------------*/
/* foreach example 4: multi-dimensional arrays */
echo '
'.'
'."foreach example 4: multi-dimensional arrays ".'
';


$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 '
'.'
'."foreach example 5: dynamic arrays ".'
';
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
/* foreach example 3: key and value */
echo '
'.'
'."foreach example 3: key and value ".'
';
$messageNav['首页'] =ROOT_PATH;
$messageNav['人才交流'] ="#"
$messageNav['动态专栏'] ="hragent/cn/"
$value):?>

> 




print out result:首页>人才交流>动态专栏