$ _POST和变量在字符串中 - 不知道为什么它不起作用

Question

I have this non-dynamic script works like this:

<p>Environment: <select name="formEnvironment" value="" >
<option value="TEST" <?= $_POST['formEnvironment'] == TEST ? 'selected' : '' ?>>Test</option>
<option value="PROD" <?= $_POST['formEnvironment'] == PROD ? 'selected' : '' ?>>Production</option>
</select></p>

---

As I have tried to make it more dynamic as possible within variables. I have problems with code within while nest and I do think it has to do with strings and variables mixing together which makes it more complicated. Any assistance with what is right way to code in that regard. I would appreciate assistance as I am only few months into PHP.

function DropDownItems($itemName, $query, $connection)
{
    $result = mysqli_query($connection, $query);

    while ($row = $result->fetch_assoc()){
        $MAS = "$_POST['form"{$itemName}"']";
        echo "<option value=\"{$row['DDVALUE']}\" ";
        echo "<?= "{$MAS}" == "{$row['DDVALUE']}" ? 'selected' : '' ?>>"{$row['DDTEXT']}"</option>";

    }
}

$itemName="Environment";
$query = "SELECT DDVALUE, DDTEXT FROM DDLISTS WHERE FIELDNAME='".$itemName."' ORDER BY DDTEXT ASC";
echo "<p>$itemName.": <select name='form".$itemName."'>";
echo "<option value=''>Select below:</option>";
DropDownItems($itemName, $query, $connection);
echo "</select>";

Answer 1

Its never a good idea to echo in functions, instead just return an array and then loop over it.

You can also break out of PHP so you don't need to do lots of echos.

So many syntax errors, so I've just rewrote it:

<?php
function DropDownItems($itemName, $query, $connection) {
    $return = [];
    $result = mysqli_query($connection, $query);
    while ($row = $result->fetch_assoc()) {
        $return[] = [
            'value' => $row['DDVALUE'],
            'label' => $row['DDTEXT']
        ];
    }
    return $return;
}

$itemName="Environment";
$query = "SELECT DDVALUE, DDTEXT FROM DDLISTS WHERE FIELDNAME='".$itemName."' ORDER BY DDTEXT ASC";
?>
<p><?= $itemName ?>
    <select name="form<?= $itemName ?>">
        <option value="">Select below:</option>
        <?php foreach (DropDownItems($itemName, $query, $connection) as $item): ?>
        <option value="<?= $item['value'] ?>"<?= (isset($_POST['form'.$itemName]) && $_POST['form'.$itemName] === $item['value'] ? ' selected' : '') ?>><?= $item['label'] ?></option>
        <?php endforeach ?>
    </select>
</p>

Be aware of SQL injections, if $itemName="Environment"; is user supplied you should change the code to use prepared queries.