PHP how to remove last separator? - php

Question

I have tried a tons of variations, but I can't find the solution. Previously the output was like this:
word a
word b
word c
etc
I have changed some parts of code and now output is:
word a | word b | word c |
How to remove last separator?
The code is:
<div id="right">
<div id="synonyms">
<?
$separator = '<span class="pipe">|</span>';
$sql = mysql_query("SELECT DISTINCT word, id_word FROM words WHERE word LIKE '$word' ORDER BY word ASC LIMIT 100");
echo mysql_error();
while ($row=mysql_fetch_row($sql))
{
$word_synonym = $row[0];
$id_word_synonym = $row[1];
$sql2 = mysql_query("SELECT DISTINCT synonym, id_synonym FROM synonyms WHERE id_word = '$id_word_synonym' ORDER BY synonym ASC");
echo mysql_error();
$num_results =mysql_num_rows($sql2);
while ($row=mysql_fetch_row($sql2))
{
$synonym = $row[0];
$id_synonym = $row[1];
$synonym2 = str_replace(" ", "+", $synonym);
echo "".$separator."".$synonym." ";
}
}
?>
</div>
I tried to add $separator = substr($separator, -1, 0); and a lot of other suggestions, but without result.

Answer 1

My preference when doing something like this is to build an array of the strings, then use implode when outputting the final string. This is particularly useful because then I can do other things like merge groups, filter them, etc.

Answer 2

This was posted before and removed, but I think it's worth including as an optional method. Although I prefer Kolink's method, I've used this, too:
Use an iterator ($i) to identify the first (or last) item.
$i=0;
while ($row = mysql_fetch_row($sql2)) {
$i++;
$synonym = $row[0];
$id_synonym = $row[1];
$synonym2 = str_replace(" ", "+", $synonym);
echo ($i>1?$separator:"").'$synonym';
}
Not part of this answer, but here's an example of Kolink's (arguably superior) method:
$links=array();
while ($row = mysql_fetch_row($sql2)) {
$synonym = $row[0];
$id_synonym = $row[1];
$synonym2 = str_replace(" ", "+", $synonym);
$links[]='$synonym';
}
if (!empty($links)) {
echo implode($separator,$links);
}