Javascript PHP变量值未显示在JS警报中

在下面的代码中，我生成了一个php表单，它接收用户的值，用于我正在处理的arp网络攻击。但是，我试图在javascript警报中显示发送的数据包数“$loops”，当我运行代码时，数据包数不会显示在警报中，我不知道出了什么问题，因此如果有人能够查看我的代码并了解其流程，我将非常感激

<form method ='post' action ="<?php echo $_SERVER['PHP_SELF'];?>">

<?php $loops = "";?>

<b> <p>Number of packets to be sent:</p>
<input type="text" name="loops" value="<?php echo $loops;?>">
<br><br></b>

<?php
$php_var = $loops;?>


<p style="text-align: center;">
<button onclick="myFunction()">Submit</button></p><br>  
<script>
    function myFunction() {
            var js_var = "The number of packets sent is: <?php echo $php_var; ?>";
                    alert(js_var);
                        }
</script>
</font>
</form>


<?php
if($_SERVER["REQUEST_METHOD"]== "POST"){
if(isset($_POST["loops"])){
    $loops=$_REQUEST['loops'];
}
?>

---

您正在将

$php\u var

分配给此处的空白

<?php $loops = "";?>

<?php $php_var = $loops;?>

因此，它没有显示任何价值

我认为您需要在文本框中获取用户输入的值

<input type="text" name="loops" value="<?php echo $loops;?>" id="loops"> // Observe the added `id` attribute.

试试看

<?php $loops = "123";?>
    function myFunction() {
      var js_var = "The number of packets sent is: <?php echo $php_var; ?> ";
      alert(js_var);
    }


函数myFunction（）{
var js_var=“发送的数据包数为：”；
警报（js_var）；
}
试试这段代码

 <form method ='post' action ="<?php echo $_SERVER['PHP_SELF'];?>">

          $loops = isset($_POST["loops"])?$_POST["loops"]:"";

         <b> <p>Number of packets to be sent:</p>
        <input type="text" name="loops" value="<?php echo $loops;?>">
        <br><br></b>

       <?php
       $php_var = $loops;?>


       <p style="text-align: center;">
         <button onclick="myFunction()">Submit</button></p><br>  
        <script>
function myFunction() {
        var js_var = "The number of packets sent is: <?php echo $php_var; ?>";
                alert(js_var);
                    }
        </script>
     </font>
       </form>


      <?php
    if($_SERVER["REQUEST_METHOD"]== "POST"){
      if(isset($_POST["loops"])){
         $loops=$_REQUEST['loops'];
    }
 ?> 

您应该始终在页面开头使用PHP。它是必需的，这样您就可以获得HTML中可用的变量

    <form method ='post' action ="<?php echo $_SERVER['PHP_SELF']; ?>">

    <?php $loops = ''; ?>
    <?php if ($_SERVER["REQUEST_METHOD"] == "POST") {
            if (isset($_POST["loops"])) {
                $loops = $_REQUEST['loops'];
            }
        }
        ?>
        <b>
            <p>Number of packets to be sent:</p>
            <input type="text" name="loops" value="<?php echo $loops; ?>">
            <br><br>
        </b>
        <?php $php_var = $loops; ?>
        <p style="text-align: center;">
            <button onclick="myFunction()">Submit</button>
        </p>
        <br>  
        <script>
            function myFunction() {
                var js_var = "The number of packets sent is: <?php echo $php_var; ?>";
                alert(js_var);
            }
        </script>
</form>


要发送的数据包数：

您应该检查变量初始化之后是否有任何
$\u请求['loops']

所以代码应该是

<?php
    $loops = "";

    if($_SERVER["REQUEST_METHOD"]== "POST"){
        if(isset($_POST["loops"])){
            $loops=$_REQUEST['loops'];
        }
    }
?>

<form method ='post' action ="<?php echo $_SERVER['PHP_SELF'];?>">

<b> <p>Number of packets to be sent:</p>
<input type="text" name="loops" value="<?php echo $loops;?>">
<br><br></b>

<?php
$php_var = $loops;?>


<p style="text-align: center;">
<button onclick="myFunction()">Submit</button></p><br>  
<script>
    function myFunction() {
            var js_var = "The number of packets sent is: <?php echo $php_var; ?>";
                    alert(js_var);
                        }
</script>
</font>
</form>


它不是从中获取插入的值吗？用户值无论如何都不会显示警报。
<?php
    $loops = "";

    if($_SERVER["REQUEST_METHOD"]== "POST"){
        if(isset($_POST["loops"])){
            $loops=$_REQUEST['loops'];
        }
    }
?>

<form method ='post' action ="<?php echo $_SERVER['PHP_SELF'];?>">

<b> <p>Number of packets to be sent:</p>
<input type="text" name="loops" value="<?php echo $loops;?>">
<br><br></b>

<?php
$php_var = $loops;?>


<p style="text-align: center;">
<button onclick="myFunction()">Submit</button></p><br>  
<script>
    function myFunction() {
            var js_var = "The number of packets sent is: <?php echo $php_var; ?>";
                    alert(js_var);
                        }
</script>
</font>
</form>