开关函数输出默认值而不是期望值

Question

我试着用下面的代码做一个简单的切换函数。

$query = "SELECT * FROM entries where Venue='Condamine' and Year='2018' and 
Event='$5,000 Novice'  and herd='2' and scratched IN('n','l')  ORDER BY Draw 
ASC";
// Execute the query
$result = mysqli_query($con ,$query);
if (!$result){
    die ("Could not query the database: <br />". mysqli_error());
}
// Change herds
function getherd($catch) { 
    switch($catch) 
    { 
        case '2': 
            return 'Herd Change'; 
        break; 
        default: 
            return 'Damn!'; 
        break; 
    } 
} 
$catch = $row["herd"];
echo "<tr>";
echo "<td bgcolor=#FFFFFF><strong> ". getherd($catch) ." </strong></td>";
echo "<td bgcolor=#FFFFFF>&nbsp;</td>";
echo "</tr>";
?>

我的结果是打印出缺省值“该死！”我做错了什么，而不是期望的值“羊群改变”。如果行herd的值= 2，我想打印出单词"Herd Change“。

Answer 1

这很可能是一个类型转换问题

试一试

$catch = string($row["herd"]);并确保$catch为2

Answer 2

您的代码应按如下方式进行更改。

<?php 
$query = "SELECT * FROM entries where Venue='Condamine' and Year='2018' and 
Event='$5,000 Novice'  and herd='2' and scratched IN('n','l')  ORDER BY Draw 
ASC";
// Execute the query
$result = mysqli_query($con ,$query);
if (!$result){
    die ("Could not query the database: <br />". mysqli_error());
}
// Change herds
function getherd($catch) { 
    switch($catch) 
    { 
        case '2': 
            return 'Herd Change'; 
        break;
        default: 
            return 'Damn!'; 
           //Break doesn't require in default case
    } 
}

//here you need to get results set from $result.
$html = "";
while ($row = mysqli_fetch_row($result)) {
     $catch = $row["herd"];

     $html += "<tr>";
     $html += "<td bgcolor=#FFFFFF><strong> ". getherd($catch) ." </strong></td>";
     $html += "<td bgcolor=#FFFFFF>&nbsp;</td>";
     $html += "</tr>";  
}
echo $html;
//It will print multiple rows, If query returns multiple rows.
?>

Answer 3

如果您的变量$catch包含整数值，则使用以下语法。

switch($catch){
  case 2:
     // your code
  default:
     // your code
}

如果是字符串值，请执行以下操作，

switch($catch){
  case "2":
     // your code
  default:
     // your code
}

Switch case manual

手动对变量进行类型转换不是一种好的做法。

我希望它能有所帮助！