PHP 显示数组键高 1 个数字

Question

我想在我的页面上显示一个数组的所有键。

现在我有这个:

$subjectcodes[1] = "Mathematics";
$subjectcodes[2] = "Physics";
$subjectcodes[3] = "Charlie";
$subjectcodes[4] = "Chemistry";
$subjectcodes[5] = "Biology";
$subjectcodes[6] = "English";
$subjectcodes[7] = "Dutch";
$subjectcodes[8] = "German";
$subjectcodes[9] = "Sociology";
$subjectcodes[10] = "Physical Education";
$subjectcodes[11] = "Art";
$subjectcodes[12] = "General Science";
$subjectcodes[13] = "Philosophy";
$subjectcodes[14] = "Management and Organization";
$subjectcodes[15] = "Research and Design";

foreach ($subjectcodes as &$value) {
        $key = key($subjectcodes);
        echo "<option value=" . $key . ">" . $value . "</option>";
}

当我使用该代码访问我的页面时，我得到:

<option value=2>Mathematics</option>
<option value=3>Physics</option>
<option value=4>Charlie</option>
<option value=5>Chemistry</option>
<option value=6>Biology</option>
<option value=7>English</option>
<option value=8>Dutch</option>
<option value=9>German</option>
<option value=10>Sociology</option>
<option value=11>Physical Education</option>
<option value=12>Art</option>
<option value=13>General Science</option>
<option value=14>Philosophy</option>
<option value=15>Management and Organization</option>
<option value=>Research and Design</option></select>

如您所见，所有键的数字都比预期的大 1。最后一个选项甚至没有 key ...

谁知道这是为什么，我该如何解决？

谢谢!

Answer 1

尝试:

foreach ($subjectcodes as $key=>$value) {
    //$key = key($subjectcodes);
    echo "<option value=" . $key . ">" . $value . "</option>";
}