删除最后一个逗号或阻止它在所有MySQL / PHP上打印

I am printing a set of words that is placed in a MySQL database and I am retrieving it with PHP. I want to present it as a comma separated list, but I need it not to print or remove the last comma. How could I do this?

I did try to use rtrim, but I did not probably do it right. This is my code as it is today:

<?php

$query0  = "SELECT LCASE(ord) FROM `keywords` ORDER BY RAND()";
$result0 = mysql_query($query0);

while($row0 = mysql_fetch_array($result0, MYSQL_ASSOC))
{
$keyword = $row0['LCASE(ord)'];

echo "$keyword, ";
?>

I did try to use rtrim, my attempt was something like this (I might be honest enough to say that I am in above my head in this ;) )

$keyword = $row0['LCASE(ord)'];
$keywordc = "$keyword, ";
$keyword- = rtrim($keywordc, ', ');
echo "$keyword-, ";

As you might imagine, this did not print much (but at least it did not leave me with a blank page...)

I usually do this by placing the results in an array first

$some_array = array();
while($row0 = mysql_fetch_array($result0, MYSQL_ASSOC)) {
   $some_array[] = $row0['LCASE(ord)'];
}

then simply:

echo "My List: " . implode(', ', $some_array);
// Output looks something like:
My List: ord1, ord2, ord3, ord4

substr($string, 0, -1);

That removes the last character.

I would do:

$keywords = array();
while($row0 = mysql_fetch_array($result0, MYSQL_ASSOC))
{
   $keywords[] = $row0['LCASE(ord)'];
}

echo implode(',', $keywords);