作业一

<?php
// 方法
$arr=[23,3,45,6,78,8,34,88,23,55];
$newarr=[];
foreach($arr as $key=>$value){
    if($key%2==0){
      array_push($newarr,$arr[$key]);  
    }
}
var_dump($newarr);
//封装函数
function getNewArrayByEeven($arr){
    $newarr=[];
    foreach($arr as $key=>$value){
        if($key%2==0){
          array_push($newarr,$arr[$key]);  
        }
    }
    return $newarr;
}
var_dump(getNewArrayByEeven($arr));
?>

作业二

<html >
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>简单的计算器</title>
</head>
<body>
<form method="post" action="">   
数1：<input type="text", name="n1" />+
数2：<input type="text", name="n2" />=
<input type="submit" name="sub1" value="计算加法" />
<p>
<?php  //这段是加法代码段
if(isset($_POST['sub1']))//这是一个点击事件，当点击了sub1时候，执行下面的代码
{
    $sub1=$_POST['n1']+$_POST['n2'];//获取将前面的两个框的值，相加赋值给$sub1;
echo $_POST['n1'].'+'.$_POST['n2'].'='.$sub1;//输出结果
}
?>
<p>
<form method="post" action="">
数1：<input type="text" name="n3" />-
数2：<input type="text" name="n4"  />=
<input type="submit" name="sub2" value="计算减法" />
<p>
<?php   //这段是减法代码段
if(isset($_POST['sub2']))
//点击事件
{
    $sub2=$_POST['n3']-$_POST['n4'];//获取相应的值
    echo $_POST['n3'].'-'.$_POST['n4'].'='.$sub2;
    }
?>
<p>
<form method="post"  action="">
数1：<input type="text" name="n5" />*
数2：<input type="text" name="n6" />=
<input type="submit" name="sub3" value="计算乘法" />
<p>
<?php  //这是乘法的代码段
if(isset($_POST['sub3'])){
    $sub3=$_POST['n5']*$_POST['n6'];
    echo $_POST['n5'].'*'.$_POST['n6'].'='.$sub3;
}
?>
<p>
<form method="post" action="">
数1：<input type="text" name="n7" />/
数2：<input type="text" name="n8" />=
<input type="submit" name="sub4" value="计算除法" />
<p>
<?php  //这是除法代码段
if(isset($_POST['sub4'] )){
    $sub4=$_POST['n7']/$_POST['n8'];
    echo $_POST['n7'].'/'.$_POST['n8'].'='.$sub4;
}
?>