PHP中foreach遍历的不仅仅是数组

foreach (array_expression as $value)
   statement
foreach (array_expression as $key => $value)
   statement

<?php
$arr = array(1, 2, 3, 4,7,8,9,10,11);
foreach($arr as $a)
{
    echo $a,'<br/>';//1 2 3 4 5 6 7 8 9 10 11
} 
?>

<?php
$arr = array(1, 2, 3, 4,7,8,9,10,11);
foreach($arr as $a => $v)
{
    echo 'key',$a,'== value',$v,'<br/>';
}
// key0== value1
// key1== value2
// key2== value3
// key3== value4
// key4== value7
// key5== value8
// key6== value9
// key7== value10
// key8== value11
?>

//定义类
class Man{
    public $name = 'LiLei';
    public $height = 178;
    public $weight = 140;
    protected $age = 30;
    private $money = 1000;
}
//实例化
$m = new Man();
//遍历
foreach($m as $k => $v){
    echo $k . ' : ' . $v . '<br/>';    //$k为属性名，$v为属性值
}
/* name : LiLei
   height : 178
   weight : 140
 */