php循环控制

PHP循环控制

数组指针
next指针下移 prev指针上移 reset指针重置 end指针所指最后一项 key读取数组键名 current读取数组键值

<?php
    //遍历数组
    //索引数组遍历
$array = ['xiaoyu','123456','1'];
    //一：for
    $arraylen = count($array);
    for($i=0;$i<$arraylen;$i++){
        echo $array["$i"],'<br>';
    }
    //二:while
    $i = 0;
    while($i<$arraylen){
        echo $array["$i"],'<br>';
        $i++;
    }
    //三:foreach
    foreach($array as $v){
        echo $v,'<br>';
    }
    //遍历关联数组
    $array2 = ['username'=>'xiaoyu','password'=>'123456','enable'=>'1'];
    //最直接的方法用foreach
    $arraylen = count($array2);
    foreach($array2 as $k => $v){
        echo $k.'=>'.$v.'<br>';
    }
    //数组指针
    //key()获取键名 current()获取数组键值
    //next()指针下移 prev()指针上移 end()最后一个指针 reset()指针复原 
    for($i=0;$i<$arraylen;$i++){
        echo key($array2).'=>'.current($array2).'<br>';
        next($array2);
    }
    reset($array2);
    $i = 0;
    while($i<$arraylen){
        echo key($array2).'=>'.current($array2).'<br>';
        next($array2);
        $i++;
    }
    ?>

<?php
    //$_SERVER 是PHP自带的系统常量
    //$_SERVER['REQUEST_METHOD']    REQUEST_METHOD是判断提交类型
    //真实环境中密码都是从数据库中读取,我们这边提前设置好;
    $user = ['username'=>'xiaoyu','password'=>'57fe40e41bacb02112fa3dd113ce4f1c'];
    if ($_SERVER['REQUEST_METHOD'] === 'POST') {
        // (!empty($_POST['username']) ? $username = $_POST['username']; : die("<script>alert('用户名不能为空');history.go(-1);</script>");
        // (!empty($_POST['password']) ? $password = $_POST['password']; : die("<script>alert('密码不能为空');history.go(-1);</script>");
        if (!empty($_POST['username'])) {
            $username = $_POST['username'];
        }else{
            die("<script>alert('用户名不能为空');history.go(-1);</script>");
        }
        if (!empty($_POST['password'])) {
            $password = $_POST['password'];
        }else{
             die("<script>alert('密码不能为空');history.go(-1);</script>");
        }
        if(!($username === $user['username'])){
            die("<script>alert('无此账号');history.go(-1);</script>");
        }
        if(!(md5(sha1($password)) === $user['password'])){
            die("<script>alert('密码错误');history.go(-1);</script>");
        }else{
            //登录成功发放session
            echo '登录成功';
        }
    }else{
        die("<script>alert('错误');history.go(-1);</script>");
    }
    ?>

手写