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php 跳出foreach / for循环实现程序Jun 13, 2016 am 10:15 AM
forforeachgphpuseseveral kindsaccomplishcyclemethodyeshavenowprogramJump out

现在在php跳出循环方法有几种,一种是使用goto另一种是使用php新特性goto命令哦,下面我来一下介绍介绍。

break是被用在上面所提的各种循环和switch语句中的。他的作用是跳出当前的语法结构,执行下面的语句。break语句可以带一个参数n,表示跳出循环的层数,如果要跳出多重循环的话,可以用n来表示跳出的层数,如果不带参数默认是跳出本重循环

//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

 代码如下 复制代码
for ($i=0;$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

goto
goto实际上只是一个运算符,和其他语言一样,PHP中也不鼓励滥用goto,滥用goto会导致程序的可读性严重下降。goto的作用是将程序的执行从当前位置跳转到其他任意位置,goto本身并没有要结束的循环的作用,但其跳转位置的作用使得其可以作为跳出循环使用。但PHP5.3及以上版本停止了对goto的支持,所以应该尽量避免使用goto。
下面的是一个使用了goto跳出循环的例子

 代码如下 复制代码
for($i = 1000;$i >= 1 ; $i– ){
if( sqrt($i) goto a;
}
echo “$i”;
}
a:
echo” this is the end”;

例子中使用了goto来跳出循环,这个例子用来检测1000以内,那些数的平方根大于29

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