连接运算符.=

$fruits = '';
while ($topic = mysql_fetch_assoc ($result)); {
    $fruits .= "{$topic["overtag "]} ";
}

// I love arrays.
$fruits = array();
while ($topic = mysql_fetch_assoc ($result)); {
   $fruits[] = (string)$topic["overtag "];
}

// If you don't want an array, but a string instead, use implode:

$fruits = implode(' ', $fruits)

您只需要将每个变量连接到循环内的变量上

$fruits = "";
while ($topic = mysql_fetch_assoc ($result)); {
  echo "{$topic["overtag "]} ";
  $fruits .= $topic['overtag'] . " ";
}
// This is going to result in an extra space at the end, so:
$fruits = trim($fruits);

哦，还有，你有一个错误的分号，它会破坏你的while循环：

while ($topic = mysql_fetch_assoc ($result)); {
                                   --------^^^--

应道：

while ($topic = mysql_fetch_assoc ($result)) {

使用下面的PHP代码，您可以从数据库表中获取数据并显示在网页上：

$sql_query="select * from yourTable";   
    $result=mysqli_query($connection,$sql_query); 
    if(mysqli_num_rows($result) > 0)
    { 
      while($row = $result->fetch_array(MYSQLI_ASSOC))
      { 
        echo "ID ".$row[0];//echo "ID ".$row["ID"];
        echo "Name ".$row[1];//echo "Name ".$row["Name"];
       }
    }
    else
    {
      echo "No Record";
    }