$sql = "SELECT * FROM 'usernames` ORDER BY RAND() LIMIT 1' ";
$result = $conn->query($sql);
while($record = mysqli_fetch_array($result)) {
foreach ($record as $d){
echo $d;
    }
   }

试试这个

$query = "SELECT * FROM `usernames` ORDER BY RAND() LIMIT 1"
$send = mysql_query($query);
while ($show = mysql_fetch_array($send)) {
    echo ''.$show['usernames'];
}

这将修复php错误：

$ts = $database->query('SELECT * FROM `usernames` ORDER BY RAND() LIMIT 1');
while ($show = $ts->fetch(PDO::FETCH_ASSOC)) {
    echo ''.$show['usernames'];
}

为了完整性，您只希望得到一行结果，因此while循环可能是多余的：

$ts = $database->query('SELECT * FROM `usernames` ORDER BY RAND() LIMIT 1');
$show = $ts->fetch(PDO::FETCH_ASSOC);
echo $show['usernames'];