Php 如何使用循环外的数组查询数据库

嗨。我尽量不在循环中放置SQL查询，因为这样可以提高性能。我想我应该使用内爆。但我不知道怎么做。这是我的密码：

<?php 

//FUNCTION CONNECTNG TO DB HERE

function turn_result_to_array($result)
{
   $result_array = array();

   for ($count=0;  $row = mysql_fetch_array($result); $count++)
   {
      $result_array[$count] = $row;
   }
   return $result_array;
}


function get_sender_username()
{
   //connect to DB 

   $query = sprintf("SELECT DISTINCT sender FROM direct_messages
                                    WHERE receiver_username='%s'
                        ORDER BY direct_messages.id DESC", 
                   mysql_real_escape_string($_COOKIE['username']));

   $result = mysql_query($query);

   $result = turn_result_to_array($result);

   return $result;

}

$senders = get_sender_username(); 

foreach($senders as $sender)
{ //SELECT IMAGE(S) FROM USER TABLE WHERE USERNAME = $SENDERS }

---

这里有一种方法：

$senderInString = implode("','",$senders);
$senderInString = "('$senderInString')";
$newQuery = "SELECT something FROM tables WHERE sender in $senderInString;"
$newResult = mysql_query($newQuery);

使用

在foreach的位置上，您还需要执行其他检查，例如无结果……等等，您正在谈论的是哪个循环？
      $query= "SELECT IMAGE(S) FROM USER TABLE WHERE USERNAME  IN (".implode(',',$senders).")";
      $result = mysql_query($query);