IF statement causing 500 Internal Server Error
<p>The IF statement below causes a 500 error.  The page loads fine when I remove the IF statement.</p>

<p>If there anything wrong with it?</p>

<pre><code>$oldtweets = mysql_query("SELECT submissionid, loginid FROM tweets WHERE submissionid = '$submissionid' AND loginid = '$loginid'");

if (mysql_num_rows($oldtweets) = 0)
{
 mysql_query("INSERT INTO tweets VALUES (NULL, '$city', '$submissionid', '$fullurl', '$uid', '$username', NULL)");
}
</code></pre>
