mysql_num_rows() return 0 when using AND

Question

I am trying to retrieve the number of rows based on this query in wordpress:

protected function wp_has_facility($fid)
{
    //global $wpdb;

    $fid = intval($fid);

    $sql = "SELECT post_id FROM wprf_postmeta WHERE meta_value = '".$fid."' AND meta_key = 'facility_id'";
    $result = mysql_query($sql) or die(mysql_error());

    $num_rows = mysql_num_rows($result);

    echo $num_rows;

    return $num_rows;
}

$num_rows returns 0 when this function is ran.

If I echo the query string and run it in phpmyadmin, it selects successfully giving me a number of rows.

After further investigation it looks like when I hardcode the meta_value it will give me a row count. But if I'm populating the string with variables it doesn't work.

Any ideas?

Answer 1

This only means your table currently contains no record that satisfies both criteria.

Remarks about your code:

Concatenation is not necessary, you may replace the query with:

$sql = "SELECT post_id FROM wprf_postmeta WHERE meta_value = '$fid' AND meta_key = 'facility_id'";

mysql_* functions are deprecated, you should avoid using them as they will be removed in a future version of PHP. Here are the alternatives .