如何說明是否選擇了選項並在下拉菜單中顯示正確的值

Question

在下方，我有一個下拉菜單，如果表單中存在驗證錯誤，它將保持下拉菜單中所選選項的顯示，否則，如果表單沒有錯誤，則下拉菜單將返回顯示“請選擇“選項：

  $validSubmission = isset($_POST['registerbtn']) isset($getyear);

    $min_year = 1;
    $max_year = 10;
    $years = range($min_year, $max_year); // returns array with numeric values of 1900 - 2012
    $yearHTML = '';
    $yearHTML .= '<select name="year" id="yearDrop">'.PHP_EOL; 
    $yearHTML .= '<option value="">Please Select</option>'.PHP_EOL;  
        foreach ($years as $year) {
            if ($validSubmission && $year == $_POST['year'] && $numrows != 1) {
                $yearHTML .= "<option value='" . $year . "' selected='selected'>$year</option>" . PHP_EOL;
            } else {
                $yearHTML .= "<option value='" . $year . "'>$year</option>" . PHP_EOL;
            }
        }

    $yearHTML .= '</select>';

上述下拉列表的值為：

1
2
3
4
5
...

10

但是我在下面的下拉菜單中使用相同的方法時遇到問題，因為下拉菜單包含兩種類型的選項，其中包含一個年份的單個數字，以及那些顯示一年中多個值且之間帶有/的選項：

1
1/2
2
2/3
3
3/4
4
4/5
5
....
10

我的問題是，如果表單中有錯誤，如何將上面的格式用於下面的下拉菜單代碼，以便使選定的選項保持選中狀態；否則，如果表單沒有錯誤，則返回顯示“請選擇”值在下拉菜單中？

 $validSubmission = (isset($_POST['createbtn']) && isset($getcourseid) && isset($getcoursename) && isset($getduration));

$durationHTML = '';
$durationHTML .= '<select name="duration" id="durationDrop">'.PHP_EOL; 
$durationHTML .= '<option value="">Please Select</option>'.PHP_EOL;  

foreach ($years as $year) {
    $durationHTML .= "<option>$year</option>".PHP_EOL;  
    if ($year != $max_year) {
         $nextYear = $year + 1;
         $durationHTML .= "<option>$year/$nextYear</option>".PHP_EOL;              
    }
}
$durationHTML .= '</select>'; 

Answer 1

嘗試這樣：

foreach ($years as $year) 
{
    $nextYear = $year + 1;

    //check for the "simple years"
    if ($validSubmission && $year == $_POST['duration'])
    {
        $durationHTML .= "<option selected>$year</option>".PHP_EOL;  
    }
    else
    {
        $durationHTML .= "<option>$year</option>".PHP_EOL; 
    }

    //check for the timespans
    if ($year != $max_year) 
    {
        $nextYear = $year + 1;

        if ($validSubmission && ($year . "/" . $nextYear) == $_POST['duration'])
        {
            $durationHTML .= "<option selected>$year/$nextYear</option>".PHP_EOL;    
        }
        else
        {
            $durationHTML .= "<option>$year/$nextYear</option>".PHP_EOL;  
        }
    }
}

即使未經測試，它也可以幫助您入門。 希望能幫助到你！