像这样的怎么样？每个数组\u pop（）都会从数组中删除一个值，因此您永远不会两次获得相同的值。

// Get your data into an array (since there's only 30 rows):
$result = mysqli_query($connection, "SELECT * FROM table LIMIT 3;");
$rows = array();
while ($row = mysqli_fetch_array($result, MYSQLI_ASSOC)) {
  $rows[] = $row;
}

// Randomise the array:
shuffle($rows);

// Get first random value:
$row = array_pop($rows);
print ($row['value']);

// Get second random value:
$row = array_pop($rows);
print ($row['value']);

// etc...