通知問題：未定義的索引

Question

我對以下代碼片段有疑問：

<div class= "main2" id ="main">
<fieldset id ='fs3'>
<form action ="<?=$_SERVER['PHP_SELF']?>" method="post">
<?php

$query = pg_query($connect, "Select name FROM types") or die("");
$numrows = pg_num_rows($query);
if ($numrows > 0) {

    echo "<br /><legend><center>Some Text:</center></legend><br />";
    echo "<center>Some Text: <select name='querySelect'>";


        while($r = pg_fetch_assoc($query)) {
            echo "<option value = ".$r['name'].">".$r['name']."</option>";
                }
    echo "</select>\t";
    echo "<input type='submit' value='submit' name='submit'>";
    echo "<br />"; 
    echo "<br />"; 
    if (isset($_POST['submit'])) { 

    $querySelect = $_GET['querySelect'];
switch($querySelect)
{
    case 'A':
        $query = pg_query($connect, "Select model FROM urzadzenia WHERE tid=1") or die("");
        break;
    case 'B':
        $query = pg_query($connect, "Select model FROM urzadzenia WHERE tid=2") or die("");
        break;
    case 'C':
        $query = pg_query($connect, "Select model FROM urzadzenia WHERE tid=3") or die("");
        break;
    case 'D':
        $query = pg_query($connect, "Select model FROM urzadzenia WHERE tid=4") or die("Zapytanie nie działa");
        break;
    case 'E':
        $query = pg_query($polacz, "Select model FROM urzadzenia WHERE tid=5") or die("");
        break;  
}
}   
else
    echo "error";

}



echo "</form>";
echo "</fieldset>"
?>

調用此代碼后，應收到以下錯誤消息：“NOTICE: UNDEFINED INDEX: QUERYSELECT”

請幫我。

Answer 1

您將數據作為 POST 發送，但嘗試從 GET 中獲取數據。

$querySelect = $_GET['querySelect'];

應該

$querySelect = $_POST['querySelect'];

更好的是，

$querySelect = !empty($_POST['querySelect']) ? $_POST['querySelect'] : null;

Answer 2

在以下行中將 GET 替換為 POST：

$querySelect = $_GET['querySelect'];