Need help incorporating "strlen"

[N!ck]

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$result = mysql_query("SELECT title, threadid, dateline FROM thread WHERE forumid NOT IN ('10','12')ORDER BY dateline DESC LIMIT 40");

while($row = mysql_fetch_assoc($result))

{
echo "<tr><td><a onFocus=\"if(this.blur)this.blur()\" class=\"cap\" href=\"java script:;\" onClick=\"opener.location='/forum/showthread.php?s=&threadid=".substr($row["threadid"],0,MAX)."'\">".$row["title"]."</a></td></tr>\r\n";

}
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Replace MAX with the maximum number of characters you want to show.