break结束当前for, foreach, while, do-while或switch结构的执行。

break接受一个可选的数字参数，告诉它有多少个嵌套的封闭结构要被断开。默认值是1， 只有直接的包围结构被断开。但是数值不能大于嵌套的层数，否则会报错.

<?php
$arr = array('one', 'two', 'three', 'four', 'stop', 'five');
foreach ($arr as $val) {
    if ($val == 'stop') {
        break;    /* You could also write 'break 1;' here. */
    }
    echo "$val<br />\n";
}

/* Using the optional argument. */

$i = 0;
while (++$i) {
    switch ($i) {
        case 5:
            echo "At 5<br />\n";
            break 1;  /* Exit only the switch. */
        case 10:
            echo "At 10; quitting<br />\n";
            break 2;  /* Exit the switch and the while. */
        default:
            break;
    }
}
?>

关键是 break 后面的参数比较牛逼!