//php当前循环为1，循环由里到外依次递增，break默认为1，例如跳出第2层循环
for ($i=0;$i<3;$i++){
foreach (array(1,2,3) as $val){
foreach (array(1,2,3) as $val){
echo "1层循环
";
break 2; //跳出第2层循环
}
echo "2层循环
";
}
echo "3层循环
";
}
//结果：
//1层循环
//3层循环
//1层循环
//3层循环
//1层循环
//3层循环