php - 无法在 while 循环之外访问 SQL 数据

Question

当我将 SQL 查询的结果保存在变量中(在 $test2 中的代码中)时，该变量在 while 循环之外为空。为什么？

通常在该循环内定义变量是有效的(参见 $test1)。 SQL 查询也可以工作。

$connection = new mysqli($servername,$username,$password,$dbname) or die("Error: " . mysqli_error($connection));
$query = "SELECT * FROM Table ORDER BY `id` ASC";
$result = mysqli_query($connection, $query);
while($row = mysqli_fetch_object($result)) {
    $test1 = "some text";
    $test2 = $row->id;
    echo $row->id // Output is the id -> works
}
echo $test1; // Output is "some text" -> works
echo $test2; // Output is nothing -> doesn't work. Why?

Answer 1

您将覆盖每次循环迭代中的变量。将它们全部保存到数组中并查看结果:

while($row = mysqli_fetch_object($result)) {
    $test1[] = "some text";
    $test2[] = $row->id;
    echo $row->id // Output is the id -> works
}
print_r($test1); 
print_r($test2);