Php 从表中选择值并按while显示？

我想通过“while”选择值，但有一个问题，代码如下：

<?php 
$following_select_article = mysql_query("SELECT * FROM follow WHERE user_follower_id='$user_id'");

while( $following_select_article_row = mysql_fetch_array($following_select_article) ) {
    $article_following_user_id = $following_select_article_row['user_following_id'].",";
    $mmnnss = substr_replace($article_following_user_id, "", -1);
    $echo $mmnss;
}

执行此操作

<?php 

$following_select_article = mysql_query("SELECT * FROM follow WHERE user_follower_id='$user_id'");
$article_following_user_id = "";
while($following_select_article_row = mysql_fetch_array($following_select_article)){

    $article_following_user_id .= $following_select_article_row['user_following_id'].",";

}
$mmnnss = substr_replace($article_following_user_id, "", -1);
echo $mmnnss;

与

非常感谢您首先给出答案，然后是编辑我的问题：）无需
substr\u替换（…）
，只需使用
substr（$str，0，-1）
substr_replace($article_following_user_id, "", -1);

substr($article_following_user_id, 0, -1);