在PHP中，将数组与MySQL表中的字段进行比较。

$servername = "localhost";
$username = "username";
$password = "password";
$dbname = "database";

$conn = mysqli_connect($servername, $username, $password, $dbname);
if (!$conn) {
    die("Connection failed: " . mysqli_connect_error());
}

$sql = "SELECT username FROM users";
$result = mysqli_query($conn, $sql);
if (mysqli_num_rows($result) > 0) {
    while ($row = mysqli_fetch_assoc($result)) {
        // 在这里处理每一行的数据
    }
}

$usernames = array("user1", "user2", "user3");

while ($row = mysqli_fetch_assoc($result)) {
    $username = $row["username"];
    if (in_array($username, $usernames)) {
        echo "Username $username exists in the array.";
    } else {
        echo "Username $username does not exist in the array.";
    }
}

mysqli_close($conn);